I also use plain Debian on my Samsung NC10 Netbook, my main problem was the 32bit CPU! Ubuntu drops/dropped 32 bit support, in Debian there seem to be no plans yet. LXDE (preconfigured OpenBox) and XFCE are working fine. But as I said, I upgraded to an SSD and to the maximum of 2GB RAM.

You can install WhatsApp and Signal in an Android emulator on the computer. We are using BlueStacks for this but there are other choices available. The emulated chat program wants to verify your phone number via SMS, just use your dumb phone and type the code by hand into the computer. That's how my wife used Option #1 and only had social media at home. But as many services that could be used with a NFC/barcode plastic card are transitioning to app only mode this gets harder :-(