Much appreciated @Christian Bundy that got me sorted!

Ended up sticking with ssb-server for now. Correction to the command issued above (host not external):

ssb-server invite.create --uses 1000 --host ssb.spadgos.com

I am, however, getting connection timeouts both when I try to hit that port in a browser and when I use it as an invite code in SSB (node reports connect ETIMEDOUT in the Patchwork terminal).

Any ideas if that is a known issue? I do believe the ports are open through the Docker firewall or I imagine I would be getting ECONNECT instead of ETIMEDOUT.

Failing that maybe I just scrap this config and go with SSB-Daemon/CLI. Any useful time-saver resources you might have on that (esp. WRT Docker) would be much appreciated!