If I have any mistakes, sorry, I am not Englishman.

Proton doesn’t have E2EE, they decrypt and then encrypt your emails. So if they do it with email, why not to repeat same thing in standard notes?Also they develop proprietary software(docs for example) and if you are interested in all proton’s problems watch mental outlaw’s video about it.

Proton will buy it, so proton will read all your notes (we remember proton’s “E2EE”)

Other alternatives: Status(https://status.app), speek!(https://speek.network), Briar(https://briarproject.org), Cwtch(https://cwtch.im) and Tox(https://tox.chat/index.html).

Obsidian and logseq

You should use it. Strong E2EE and fully open source(unlike mega). Also bult-in notes and chats. 👍

Or if you have a lot of money - StartMail. It has unlimited aliasing feature and UI is very good.

Maybe kMail(very beautiful) or disroot(more about freedom and not very beautiful). Both open source.

StartMail, Soverin, Disroot, Infomaniak Kmail, Mailfence, Mailbox.org, Kolab Now And Posteo

Use any matrix client unstead.