It seemed like it was written in docs that proot development is halted.. However, some forks are still in active development, it might be worth looking at code of repos such as termux/proot for potential improvements.

Also, is it possible to provide junest as an app for Android? It seems it can be helpful in terms of project funding, by keeping some addons for small price, say like a donation v

Specifying a file name for --sudoers-file or --unit-file places them in the same directory as the openvpn config file rather than in /etc/suders.d/ or /etc/systemd/system/