Can't you use Aurora Store?
F-Droid
F-Droid is an installable catalogue of FOSS (Free and Open Source Software) applications for the Android platform. The client makes it easy to browse, install, and keep track of updates on your device.
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The F-Droid repo has the VPN , and the Izzy repo has Mail
What is the Izzy repo? Is it trustworthy?
It's a repo of github releases. They aren't compiled like f-droid releases are. With f-droid, there's another set of eyes looking at things before they get to you. With Izzy, you have trust each individual dev. I prefer f-droid, but I use Izzy releases when the program is preferred, or there's no f-droid equivalent.
Does that mean since it comes from Proton's Github page, then it should be pretty trustworthy? Or at least as trustworthy as getting the apps directly from Proton?