If you’re using Gmail, and you’re considering alternatives for privacy reasons, then 100% without a doubt, objectively and unequivocably, Proton is the better choice of the two.
There are other email providers with privacy assurances, and yes, you can self-host, but don’t let perfection be the enemy of the good.
To address the trustworthiness of Proton directly: I’ve been a Proton user for about 10 years. It gets the job done. I have complaints, but privacy is not among them.
I’ve installed Debian Linux on over 50 devices by now. A vanilla configuration with GNOME works pretty much out of the box for me on a high-end desktop with a modern NVIDIA graphics card.
I’d say the biggest part of the learning curve is figuring out which apps are good and suitable for what you’re trying to do. Just like with Windows and macOS and Android and iOS, there’s only a handful of viable options among an overwhelming sea of poor ones.
There are many wrong ways to install NVIDIA on any given Linux distro and architecture, and only one functional way. As others here are saying, that’s on NVIDIA, not you or Linux.
General advice: whenever possible, strongly prefer your distro’s standard package manager to install things over any other method. With Ubuntu, I believe that’s either apt or snap.
Also: if you find yourself poking around in some obscure system internals while troubleshooting an issue, you probably took a wrong turn somewhere.