It was OpenVPN with a TOTP 6 digit google authenticator MFA code. It worked just fine with Tunnelblick in MacOS and Viscosity in Windows, but I never found a setup that worked in Linux. And I searched for a while. I had to switch away from linux because there was no good solution to this.
And it's not the only non-easily fixed issue I've had with Linux over the years. The classic saying is "Linux is only free if you don't value your time" and I've found that to be true.
Funny that I am here since I am a relatively mid tier IT guy and not a developer.. but have you considered a windows PC with a Linux VM sharing the VPN connection? Even when there are possible restrictions around that, I am sure an enterprising developer such as yourself could find a way around that, yes?
Why would I want to do that? I said in the beginning of this thread that my tools work on all 3 major OS's (Windows, MacOS, and Linux). A VPN I need doesn't work on Linux? I'll just use Mac or Windows, which is what I did. That was 5+ years ago now.
> I prefer the latter by rather a lot.
Good for you. I'll keep looking for a good way to set up a work vpn in Linux.