Ah right okay.

The Android version of Signal works well in Waydroid in Ubuntu Touch also, bu running it permanently in the background like Signal is designed to do is problematic for several reasons that make it kind of a painful proposition. But if I needed it just to send or receive a message punctually, it would be a great solution.

Okay then, it sounds like Whisperfish might work well enough as a primary Signal client to make SailfishOS worth giving a spin. Thanks!