Unfortunately updates are required here; to support new PHP versions. To the best of my knowledge the current version of Adminer still is not fully compatible with PHP 8.0 (it will emit warnings into an exported SQL dump):

https://github.com/vrana/adminer/pull/429 https://github.com/TimWolla/docker-adminer/issues/108#issuec...

Disclosure: I'm the TimWolla of the repository in the second link :-)