Difficulty building RTAI linuxcnc from source

I think that you will need to do the ./debian/configure again to get the new list of dependencies for 2.8 (sorry).

Try ./debian/configure -r first, as I think that still works in 2.8 and means "configure for the current running kernel". Note that this only configures for creating debian packages, which you probably won't end up doing. But it should get a more accurate list of dependencies.

When I do ./debian/configure -r I get "your kernel is not known ...

When I do ./debian/configure I get a list of options to append, but choosing the option of explicitly naming the kernel (and then doing so), I'm back to "your kernel is not known."

Googling the yapps error, I see there is plenty of forum history with it ... but I don't see a consensus solution in the posts.

Thanks.

try
sudo apt install yapps2

Thanks for the suggestion ... here's the result:
robert@debian:~/linuxcnc-dev$ sudo apt install yapps2
[sudo] password for robert:
Reading package lists... Done
Building dependency tree
Reading state information... Done
yapps2 is already the newest version (2.2.1-3).
0 upgraded, 0 newly installed, 0 to remove and 183 not upgraded.

if I re-run make after getting that result, in bombs in the same way in the same place.

You have an older version of Debian, did you try without 2, although i doubt it would change anything, but it might as there is also python-yapps that goes with it, but in my case it is for python3-yapps2.
try also
sudo apt install python-yapps python2-yapps python-yapps2 python2-yapps2 python3-yapps2
and remove any of those that it complains about.

Wow! Thanks.
One of those first two worked, either sudo apt install python-yapps or sudo apt install python2-yapps. I ran all the other variations just in case, but they didn't do anything.
So, having gotten some yapps action, I tried make again ... and ... it worked! So much verbiage scrolled by in my command window I can't go back and see which of the two early yapps commands was the one that worked. I remember it was early in the sequence, your first or second suggestion.
After make succeeded, I did sudo make setuid then
./scripts/rip-environment.
I typed linuxcnc and it ran ... until it errored out not being able to recognize the Motenc-Lite board on the PCI bus, which was as far as I got with the packaged version of linuxcnc.
Now though, because I can build, I can uncomment the line that prints out the board type number. The code is prepared for the board type to be 0 or 1, nothing else. A good starting point for troubleshooting board type recognition will be to know what value the code is seeing.
I thought I set the board jumpers correctly and/or cycled through all the jumper combinations, but maybe not.
Thanks again.