As previously announced we have now moved the MariaDB :alpine tag to :latest and deprecated our Ubuntu-based image. No user action is required when updating to the new tag, but as ever we recommend ensuring you have a proven backup of your data before performing any updates. Going forward, the :alpine tag will not receive any further updates.
If for some reason you need to remain on the old version, you can pin your install to the version-110.4.21mariabionic tag, although please be aware that no further updates will be provided for it.
latest or branch (develop, nightly, etc.) tags and will need to use a specific version tag if you still need access to the image. You can read more about this here.