I only close by browser for updates, so I use Cookie AutoDelete which removes cookies when the tab is closed. That said, I still instinctively reject cookies when given the option.
Signal is easy to on board folks to. Not a huge fan of the phone number requirement, but it's worth the trade off for me. I used Session for a while, but media sharing was buggy. I've heard good things about Simplex, but the inability to have a desktop client was deal breaker for me.
CalyxOS did/does too