I’m very happy with fastmail for a similar use case to OP. Definitely a strong +1 fron me!

Of course you could just write on a sticker with a pen, but where’s the fun in that!

To be fair I don’t think that can be entirely prescribed to drop in user base; the internet ad market in general is absolutely tanking at the moment.

We’ve seen similar embrace, extend, extinguish with protocols before. It reminds me of XMPP, which used to be the defacto chat protocol and once upon a time you could use self-hosted providers to chat directly with people on things like Google Talk. Obviously once enough people were on Google Talk, they switched the protocol to a propriety protocol and XMPP basically died.

The lesson is that if you want a protocol to be resilient then you want to avoid corporations having a majority user share on it.