bootloader
Thank you for revealing and discussing this issue in Proton email (and others) apps.
FWIW, I've been quite satisfied using Vanadium to access my various Proton online storage(s), and AFAICT Google is not involved.
Also Vanadium seems the MOST trustworthy and secure (hardening) web app around. Even if Proton modifies its' apps, they won't be as secure as Vanadium. So for me, the question becomes, how badly do I need push notifications?
Don't need them.
Also, the quick-reply business crowd seems to be moving to SMS - which of course has NO privacy - but significant security thanks to GOS auditing and hardening.
(FWIW this same reasoning applies to my banking - I use Vanadium, and not some poorly-written bank app)
Just suggesting that you do not abandon Proton web storage(s). HTH.