I was hit by this too today since the mariadb:latest docker image got bumped to 10.6.3. 
Doing a image: mariadb:10.5 helped!
See: mariadb needs to be locked to 10.5 路 Issue #1536 路 nextcloud/docker 路 GitHub
I was hit by this too today since the mariadb:latest docker image got bumped to 10.6.3. 
Doing a image: mariadb:10.5 helped!
See: mariadb needs to be locked to 10.5 路 Issue #1536 路 nextcloud/docker 路 GitHub