ran into something like this on openHABian too. that “Username for https://github.com” usually means the git fetch for the openHAB branch is getting auth-challenged (rate limit / credential helper / remote url flipped) and openhabian-config just hangs waiting on stdin.
what worked for me once was ctrl-c out of it, then as root: cd /opt/openhabian && git remote -v && git status
if origin is GitHub - openhab/openhabian: openHABian - empowering the smart home, for Raspberry Pi and Debian systems · GitHub try a plain fetch: GIT_TERMINAL_PROMPT=0 git fetch --dry-run origin
if that also asks for a user, set the remote to the public https url again or temporarily skip the branch check. sometimes just waiting a bit and retrying clears a github anon rate limit.
not 100% sure its the same on 5.2.1 but the stuck prompt is almost always that git step, not your openhab runtime.
this forces git to use the old http protocol, which somehow goes around the blockage of the authentication. Make a check before how your git is configured so you can revert it back to the original state.
I have two openhab installations, both run version 5.2.1. When I input sudo openhabian-conifg one installation worked normal (without asking for github username, the other installation aksed.
I aborted with ctrl-c and tried again a couple if minutes later. The second try also github username was asked for. But on the third try (wihout changing anything) it suddenly run without asking.
So i suggest just try again, it may ask again but suddenly it will work
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