Yeah, sure. But Matrix is decentralized and federated. So you can pretty much join any instance and be able to talk with anyone on any instance. So why not select another instance ~~or maybe even self host one yourself?~~
edit: didn't read the text till the end
Ok, the post feels like it's made by an LLM, that's why.
Posteo supports PGP encryption with a PGP key you have when an email comes into your inbox, which then can be decrypted by your client. So it is doable.
Yet not great from a privacy perspective. They don't even allow third party email apps.
KDE Plasma just keeps getting better every single week.
So XMPP?
"functions on android"
You can download the website's static files then (html, css, images, etc.) but features such as search won't function if it works by querying some database.
Iirc most browsers have a way to make website's available offline. I know chromium has it, but firefox does not. You'd probably need an extension for that. Or you can download the static files, store them in a directory manually and then open the index.html with firefox. That should work.
Would you be ok with reading wikipedia?
There's this app that is for viewing wikipedia pages both online and offline: https://f-droid.org/packages/org.nsh07.wikireader/
Truly amazing technology. What a time to be alive!