Regarding the Proton controversy: If you need private communications you should be avoiding email at all costs. SMTP, the standard that lets email clients interoperate, make it impossible to encrypt the metadata at all. This isn't the first time Proton has been forced to hand this data over by their government (Not the FBI), and it won't be the last.
Also, By Default on YouTube puts it best:
"If you have a personal librebooted OpenBSD email server in an unregistered nuclear bunker with a crypto domain connected to Tor and blurred out on Google Maps, The other half your email went across some ISP network and is just sitting on someone else's email server."
