I tried SimpleX but the VPN kill switch on my phone prevents syncing with my computer.
I use telegram primarily as a note taking app with sync features.
Occasionally I send files to friends, so having easy set up for tech illiterate would be great.
Unfortunately the Signal recommended by many people may not work for you, it cannot work on multiple mobile devices at the same time, for example on a smartphone and tablet.
I don’t understand why no one recommends Jami? It’s the only messenger that works without a server at all. And yes, it has the ability to forward messages to itself (to use as a note) and works on any devices at the same time.