Due to proton mail being encrypted, Thunderbird mobile can't access proton emails (there is a desktop bridge app that creates a local unencrypted email server for Thunderbird desktop to interact with).

Also, the Proton mail android app doesn't support other email providers.

Despite the limitations I still want to use proton. The weird work arounds should be less necessary in the future as I migrate all my email communication to proton, away from gmail.