Now we are getting somewhere: I am not sure if Docker supports nftables… (see: https://github.com/moby/moby/issues/26824). But on the other hand we have issues that complain about nftables beeing slower? see: https://github.com/moby/moby/issues/39590
From what I remember the recommended fix for Debian Buster with nftables was to switch back to iptables.
I wasn’t aware Ubuntu switched to nftables on 20.04 as well.