16 years old? That thermostat has sure had a run, must have been designed pretty well to last this long without some electronic failure.
Assuming it's cloud connected, anyone aware whether it got updates for the newer versions of TLS and root certificates? As an example I'm aware quite a lot of android and similar devices from that era have expired certificates now, and outdated/vulnerable SSL libraries...
Edit: Edit example
ElementaryOS sounds like a perfect fit for you, if you haven't tried it already. Superb gesture support and consistent UI across all built in apps
That said, a lot of the gesture support has been implemented in Gnome and KDE now anyway, particularly partial gestures which previously had very poor support IIRC