Does DECnet for Raspberry Pi work with Ubuntu 21.10
(Linux 5.13 for x86)?
Are you talking about John Forecast Raspbian port?
https://github.com/JohnForecast/RaspbianDECnet
It would very likely work on x86, but somebody would have to build it all and maybe fix a
few odds and ends. Remember that Raspbian is based on Debian which, although closely
related to Ubuntu, is not exactly the same.
As with all things Linux, it's guaranteed not to work out of the box, but with some
effort it can be made to work eventually.
Bob