4.x to 5.x upgrade - "Linux release not officially supported"

I just upgraded a template I have on openHABian, on a new R-Pi 4 from 4.3.7 to 5.1.3 and get this error. It’s 64 bit (“aarch64” showing at the top when I login through Putty). Release shows as bookworm.

So this error seems incorrect. Can anyone tell me what the problem is? I upgraded the system through option 2 of the openHABian console thinking that there might be some old packages triggering this but I’m still getting the error.