Proton VPN for Ubuntu Linux runs slowly and frequently displays “the application is not responsible, wait or quit” messages.
I am a new Ubuntu user this year and recently installed Proton; but, when I use it, it slows and becomes sluggish at times. What to do?
Works fine on Linux Mint for me.
Welcome to the world of Ubuntu! 
It can be a bit tricky at first, especially with stuff like VPNs. I’ve had similar issues with ProtonVPN on Linux. The “application is not responding” messages are super frustrating. It could be a compatibility issue with how ProtonVPN is running on your system.
Yeah, ProtonVPN can sometimes be a bit sluggish on Linux, especially if you’re using the official GUI. You might want to try using WireGuard instead of OpenVPN—it’s faster and often more reliable on Linux. You can set it up manually with ProtonVPN. 
Totally agree with switching to WireGuard! I noticed a big performance improvement after doing that. ProtonVPN’s official app can be a bit heavy, so I actually switched to using the command line (CLI) version of ProtonVPN on Ubuntu. It’s way faster and much more lightweight. 
If you’re new to Ubuntu, setting up WireGuard or using the CLI might feel a little intimidating, but there are plenty of tutorials online. Just open your terminal and follow the ProtonVPN Linux guide. It’ll get you up and running smoothly. And yeah, the CLI version is way less prone to freezing compared to the GUI! 
I’m using version 24.01.1 and set ProtonVPN to auto-launch at startup. It’s working smoothly. I followed the steps here (skipping the tray icon part): ProtonVPN Ubuntu Guide. Try connecting to a different server by default, that might help.
Same here, installed it as per the guide, no issues at all.