Things just keep getting stranger… I just installed Eoan fresh on one of my machines, installed updates, installed the drawing snap - works perfectly. No issues whatsoever.
UPDATE:
Alright, the snap started core dumping on the above machine.
I’m pretty sure the iso I used to install was a daily build from 12th October, so it struck me that perhaps one of the seeded snaps that came with the iso was working and subsequently broke with a refresh some time after.
I noticed that the gtk-common-themes snap updated from 1313 to 1353 so, considering the theming issues we saw, I tried a snap revert gtk-common-themes, and yeah, fixed, no more crash.