Compatibility TYPO3 v12.4 LTS.  
This release is 100% deprecation-free!
Read the release article here: https://docs.typo3.org/p/mask/mask/main/en-us/ChangeLog/8.1/Index.html

Upgrade Wizard necessary
The persistence / matching of type Content fields has changed. It is necessary  
to run the upgrade wizard with the title Migrate Mask Content fields.

Command with TYPO3 CLI:
// composer mode
vendor/bin/typo3 upgrade:run migrateContentFields

// classic mode
typo3/sysext/core/bin/typo3 upgrade:run migrateContentFields