Yes pp-vpn will not install on the 20.04 ubuntu family of Linux OS with a new install as it requires python2.7 with "python-request".
If one has a working 19.* ubuntu family OS it maybe possible to do an upgrade to 20.04, but if the upgrade removes python2.7 stuff,
the result maybe more grief.
PP-VPN needs to be upgraded to work with python 3.* or rewritten to not use python.
Nord VPN can be manually installed on 20.04 ubuntu family OS as a temporary fix, but it lacks the nice features of PP-VPN.
Please fix PP-VPN NOW !!!