While the "mail.protonmail.com" and "old.protonmail.com" do not seem to work with Wayfarer, I was able to login via the "beta" page of Protonmail "beta.protonmail.com". But unfortunately there are severe problems:

1) Logging is extremely low, taking several minutes!

2) Opening the "inbox" does not work prpperly... The messages cannot be shown, only some empty boxes instead of them. And there appears at regular intervals an error message:" Request timed out".

Can these problems be fixed? Is there possibly a problem with the encryption method used in Protonmail, slowing down everything...?

It would be important to get Wayfarer to work with Proton as there are no other choises for PPC (Browsers for PPC Linux do not work at all!)

It's unlikely this will get better. From what I can see, Proton does elliptic curve crypto in pure JavaScript (and may even switch to WebAssembly for that). I bet it's simply too slow and the Promises time out before this is processed - assuming it'd work in first place, since that stuff is screaming endianness issues to me. Unfortunately, the recent advancements in JavaScript were done by people ignoring the existence of Big Endian.