You need to be able to have multiple nodes in one LAN access ports on each others’ containers without exposing those to the world and without using additional firewalls in front of the nodes.
That’s why kubernetes ended up removing docker support and instead recommends podman or using containerd natively.
Fdroid only gained the ability to auto update apps a while ago, so that’s why you got that prompt.
Also, if the permissions an app requests change, fdroid can’t always auto-update it.