So...the day after I decide to shift from Facebook and Messenger and start telling people I'm on Signal...
I suddenly fix the issues with using it via Wayland on Linux. Buttery smooth now.
Signal release an update (7.5.1) that clears up one of my longest-standing bug-bears about their Linux Client - no Minimise-to-Tray. Using it meant keeping an active window open at all times. Now it tucks away out of sight like all other chat apps!
It's suddenly ready to receive all these new folks. 😍