Your tone and your assumption that everyone else is an idiot is irritating.
The key part of your first sentence is “via Proton”. Support for client side gpg is easy and they’re not doing it either out of some strategic play or purely out of stubbornness. Working on standarts is great! I’ve had a “Visionary” subscription to Proton for years, since before the VPN and all the extra stuff. I like the company, overall. But, as mentioned in my first comment, this is the singular most annoying part of their service to me.
Looks good in principle! I’ve yet to try using it with anybody.