yes, it is possible. at the very least you could do a setup.py installation, which would avoid ubuntu package names
perhaps ubuntu renamed 'python-configobj' to 'python2-configobj'?
if you installed configobj using pip, then you *should* be able to use the '-f' option to tell apt to ignore the dependencies
the package names in ubuntu have always varied a bit from those in debian. sometimes that makes it slightly annoying to build a single package that works everywhere, sometimes that makes it impossible.
"end of life" for python2 does not really matter. the software will continue to work. as long as it does what you need, keep using it.
fwiw, i have weewx systems that will NEVER see python3 - python2 works just fine and the hardware does not have the resources for python3. i know a space telescope that is running python2 and will never get an upgrade (if you think its hard to update a NAS or router, try doing a satellite - i have great respect for the folks who keep spacecraft operational well beyond their designed mission :). the ground systems probably will not get changed over to python3 for at least another couple of years, and that will only be due to dependencies on scipy, numpy, matplotlib, and the need to use some recent AI and optimization techniques that are only in python3.
m