Native CAM can't open

No

depending upon how you installed nativecam it asks you if you have a run in place or full installed linuxcnc install.

I suspect that is the issue.

note the nativecam won't work with master 2.9 or bullseye as it is still python2 and GTK2... and these are no longer used with mater / 2.9 or bullseye... so it simply doesn't load

I have just looked again at the screenshot and you have 2.9 listed. that will be the problem.

nativecam will run with 2.8.2 just fine on buster. but not on bullseye

Could be possible to run Nativecam standalone without any Linuxcnc install on another linux box like manjaro ..because any package done for Nativecam on manjaro ?
Because if i start ncam with -t and any linuxcnc runing it start standalone on the Linuxcnc stretch box ..
This will be very nice To be able to create program on another computer than the one with Linuxcnc install..