about:./configure --with-realtime=uspace

Cant do this anymore bye all wrote:

What version of Debian did you sue ?

Just in case someone else has the same issue.

This issue may be caused by having too many versions of Python myself. I used a newly installed Debian 10, and this issue did not recur.
www.linuxcnc.org/iso/linuxcnc-2.8.4-buster.iso

Thanks mate, good you got it resolved, sorry it took so long to figure out. And thanks for sharing.