Symfony 6.1.0-BETA1 has just been released.
Here is the list of the most important changes since 6.0:

feature #44798 [FrameworkBundle] Integrate the HtmlSanitizer component (@tgalopin, @wouterj)
feature #46045 [Translation] Improve LocaleSwitcher a bit (@nicolas-grekas)
feature #42403 [Validator] Define which collection keys should be checked for uniqueness (@wkania)
feature #44405 [Routing] Allow using services in the route condition (@renanbr)
feature #46009 [FrameworkBundle] Add support for first-class callable route controller in MicroKernelTrait (@fancyweb)
feature #44155 [FrameworkBundle] Add semaphore configuration (@jderusse)
feature #45803 [Routing] Add EnumRequirement to help generate route requirements from a BackedEnum (@fancyweb)
feature #45724 [FrameworkBundle] Add support to set BinaryFileResponse::trustXSendfileTypeHeader over config (@alexander-schranz)
feature #45092 [HttpFoundation] Send Content-Length when calling Response::send() and the content is a non-empty string (@nicolas-grekas)
feature #45967 [Messenger] Consume a PSR-14 dispatcher for dispatching events (@derrabus)
feature #45951 [Notifier] [OvhCloud] Add no_stop_clause to DSN (@alamirault)
feature #45795 [ExpressionLanguage] Add support for null-safe operator (@mytuny)
feature #45605 [Form] Add prototype_options to CollectionType (@michaelKaefer)
feature #45912 [ExpressionLanguage] Add some more operators (@fabpot)
feature #45656 [Serializer] Add serializer profiler (@mtarld)
feature #45072 [Validator] Allow creating constraints with required arguments (@norkunas)
feature #43239 [Finder] Look for gitignore patterns up to git root (@julienfalque)
feature #45845 [TwigBundle] Pre-compile only *.twig files in cache warmup (@GromNaN)
feature #44446 [Mailer] Improve extensibility of EsmtpTransport (@ampaze)
feature #45226 [PhpUnitBridge] Add option ignoreFile to configure a file that lists deprecation messages to ignore (@mondrake)
feature #43163 [Messenger] Add Redis Sentinel support (@norbertschultheisz)
feature #43701 [HttpKernel] Simplifying Bundle/Extension config definition (@yceruto)
feature #45873 [HttpFoundation] Allow dynamic session „ttl“ when using a remote storage (@nicolas-grekas)
feature #45878 [DependencyInjection] Add argument type closure to help passing closures to services (@nicolas-grekas)
feature #44898 [Ldap] LDAP authentication should return a meaningful error when the LDAP server is unavailable (@Jayfrown)
feature #45090 [Validator] Improve Image constraint invalid mime type message (@fancyweb)
feature #42997 [Cache] Improve reliability and performance of TagAwareAdapter by making tag versions an integral part of item value (@Sergey Belyshkin, @nicolas-grekas)
feature #45512 [DependencyInjection] Allow using expressions as service factories (@nicolas-grekas, @jvasseur)
feature #45273 [Messenger] Allow AsMessageHandler attribute on methods (@mjpvandenberg, @fabpot)
feature #44284 [SecurityBundle] Display the inherited roles of the logged-in user in the WDT (@jmsche)
feature #44303 Add Engagespot bridge (@danut007ro)
feature #44532 Handle CSV DSN in ZookeeperStore (@qkdreyer)
feature #45047 [Notifier] Use Importance level to set flash message type (@benr77, @fabpot)
feature #45166 [HttpFoundation] add stale while revalidate cache header (@remieuronews)
feature #45195 [Notifier] Add Sendberry notifier bridge (@StaffNowa)
feature #45793 [FrameworkBundle][Translation] add LocaleSwitcher service (@kbond)
feature #45833 [HttpKernel] Add Http Status 423 LockedHttpException (@xosofox)
feature #45705 [FrameworkBundle] Deprecate the messenger.reset_on_message config option (@upyx)
feature #45812 [HttpClient] Improve default content-type handling (@nicolas-grekas)
feature #45783 [DependencyInjection] adjust Autowire attribute implementation (@kbond)
feature #44171 [Config] Add comment on array methods (@jderusse)
feature #45657 [DependencyInjection] add Autowire parameter attribute (@kbond)
feature #45725 [Finder] Fix SplFileInfo PHPDoc (@InvisibleSmiley)
feature #44948 [Console] Add completion values to input definition (@GromNaN)
feature #45745 [ErrorHandler][HttpKernel] Read SYMFONY_IDE to render exception in case of fatal error (@GromNaN)
feature #45765 Mailer – Display email recipients in Profiler (@raziel057)
feature #45094 Add generics to ArgumentMetadata::getAttributes (@Seldaek)
feature #45761 Throw access denied if CurrentUser cannot be resolved instead of a 500 (@Seldaek)
feature #45680 [DependencyInjection] use #[Required] for ServiceSubscriberTrait::setContainer() (@kbond)
feature #45624 [Config] Allow using environment variables in EnumNode (@ecourtial)
feature #45484 Make constraint violation interfaces stringable (@HypeMC)
feature #43931 [HttpClient][WebProfilerBundle] Add button to copy a request as a cURL command (@Deuchnord)
feature #45515 [BrowserKit] Add toArray to Response (@HypeMC)
feature #45658 [Routing] Avoid double encoded slashes in query parameters (@usu)
feature #45062 [PropertyInfo] Add PHP 8.0 promoted properties @param mutation support to PhpDocExtractor (@raphaelvoisin)
feature #44522 [Messenger] add TransportMessageIdStamp to RedisSender (@GaryPEGEOT)
feature #45623 [Validator] Deprecate constraint „ExpressionLanguageSyntax“, use „ExpressionSyntax“ instead (@mpiot)
feature #45563 Deprecate requiring the „symfony/symfony“ package (@nicolas-grekas)
feature #45616 [HttpClient] Remove credentials from requests redirected to same host but different port (@GromNaN)
feature #45377 Bump minimum version of PHP to 8.1 (@nicolas-grekas)
feature #45421 [Translation] Add the possibilty to export xliff translation with the .xliff suffix (@DanielBadura)
feature #45152 Ability to customize payload when sending mail through mailjet+api (@gam6itko)
feature #44665 [HttpKernel] Add the UidValueResolver argument value resolver (@fancyweb)
feature #44073 [ExpressionLanguage] Support lexing numbers with underscores and decimals with no leading zero (@fancyweb)
feature #44721 [Serializer] Deprecate support for abstract uid denormalization in UidNormalizer (@fancyweb)
feature #44615 [Routing] Support the „attribute“ type (alias of „annotation“) in annotation loaders (@fancyweb)
feature #45265 [HttpKernel] Add Profiler::isEnabled() method (@Bilge)
feature #45449 [Mime] Added getter for „TextPart::$name“ (@MasterRO94)
feature #45402 make Message classes extensible (@bitgandtter)
feature #45476 [HttpKernel] Deprecate StreamedResponseListener, it serves no purpose anymore (@nicolas-grekas)
feature #45436 [Messenger] Support setting connection_name for AMQP (@a.dmitryuk)
feature #45450 [DependencyInjection] Add an env function to DI expression language (@jvasseur)
feature #45388 [Mailer] Allow manually start() of SmtpTransport (@jannick-holm)
feature #45376 [Mime] Fix embed logic for background attributes (@flack)
feature #45360 [ErrorHandler] trigger deprecations for @final properties (@nicolas-grekas, @fancyweb)
feature #45371 [Validator] Deprecate Constraint::$errorNames in favor of Constraint::ERROR_NAMES (@nicolas-grekas)
feature #44692 [Cache][FrameworkBundle] add cache:pool:invalidate-tags command (@kbond)
feature #45361 [Console] Deprecate the $defaultName property (@derrabus)
feature #45313 [Cache] Add support for ACL auth in RedisAdapter (@gam6itko)
feature #45303 [ErrorHandler] Report overridden @final constants (@fancyweb)
feature #44484 [Translation] [Loco] Send If-Modified-Since header when possible (@Kocal)
feature #45307 [Mailer] Allow manually stop() of SmtpTransport (@dvaeversted)
feature #43973 [Serializer] Add context builders (@mtarld)
feature #45222 [Mailer] Implement EmailTags for Amazon Mailer (@driesvints, @kbond)
feature #44670 [SecurityBundle] Allow to specify a RequestMatcher directly in an ACL definition (@TristanPouliquen)
feature #45139 [Notifier] smsapi-notifier fast option to sending message with the highest priority (@marphi)
feature #45155 [Serializer] Set context annotation as not final (@benjaminmal)
feature #44503 [FrameworkBundle] Allow PHP configuration in config/packages by default (@dreadnip)
feature #45101 [Form] Add inputmode attribute on NumberType (@welcoMattic)
feature #45075 [Routing] Enrich MissingMandatoryParametersException (@adrienlucas)
feature #45064 [Messenger] Add sessionToken option to SQS transport (@filkaris)
feature #44917 [Mailer] Add downloadable attachments to profiler (@dbrekelmans)
feature #45054 [Routing] Allow using UTF-8 parameter names (@nicolas-grekas)
feature #44360 [Notifier] [Bridge] [KazInfoTeh] added the bridge (@taranovegor)
feature #44874 [Notifier] Added 46elks notifier bridge (@jongotlin)
feature #44913 [Notifier] Add Orange SMS bridge (@enigma972)
feature #44971 [Messenger] Resolve handled classes when only method in tag is provided (@angelov)
feature #43982 [Messenger][Serializer] Deprecate „context aware“ interfaces (@mtarld)
feature #44790 [Serializer] Give more hints when an attribute is not correctly used (@lyrixx)
feature #44831 [HttpKernel] Add a controller argument resolver for backed enums (@ogizanagi)
feature #44589 [Messenger] add SerializedMessageStamp (@nikophil)
feature #41750 [Yaml] Double-quote strings with single quote marks (@Ostrzyciel)
feature #44774 Add exclude to TaggedIterator and TaggedLocator (@ruudk)
feature #44681 [HtmlSanitizer] Introduce HtmlSanitizer component (@tgalopin)
feature #44311 [Mime] add DraftEmail (@kbond)
feature #44746 [Console] Add method __toString() to InputInterface (@boesing)
feature #44568 [HttpClient] Allow yielding Exception from MockResponse’s $body to mock transport errors (@fancyweb)
feature #44672 [Translation] Translatable parameters (@sylfabre)
feature #44451 [PropertyInfo] Add support for phpDocumentor and PHPStan pseudo-types (@EmilMassey)
feature #44575 [Framework] Read env var SYMFONY_IDE by default for framework.ide (@GromNaN)
feature #43641 [Console] Issue 43602 : Add fish completion (@guillaume-a)
feature #44150 [Assets] Accept empty base_url, in order to simplify local dev configuration. (@GromNaN)
feature #44137 [Mailer] [Mailgun] Allow multiple TagHeaders with MailgunApiTransport (@starred-gijs)
feature #44543 [HttpFoundation] Update cookie date time format (@chapterjason)
feature #44483 [HttpKernel][WebProfilerBundle] adding xdebug_info page to webprofilerbundle (@chr-hertel)

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