Dual boot is still the best and simple way to go dip a little into Linux so that’s quite good already! 
Fedora is also quite stable and cool to use, hence should be a good choice.
As for gaming, depends on the games you’re interested in but ProtonDB is a good resource to see if a game can be run out of the box on Linux or not. Most solo games (as in no e-sport like League of Legends) should run just fine.
And yes, Nvidia drivers on Linux are a huge pain last time I tried too.
Meanwhile some distros ease that one, like Bazzite!
I went through a similar decision path just recently and updated an answer of mine, in case you want a starting point.
I guess this feature is seen as a “nice to have” and not necessary by the companies, hence why the support is spotty. 
The CLI does that quite well: How to use the Proton VPN Linux CLI | Proton VPN
It’s a company, it will work on things that bring in the money and not the 0.5% of users using the product in niche ways. I know it’s unfair and I don’t like it either but that’s the state of Linux as of today, if it ever becomes more popular it might change!
Isn’t that more of a soft phone software problem? What do you use as your client? Linphone, Jami or something else?