Okay, think I've found a fix!
I noticed that even when just sat in the settings menu not doing anything, Skate's system RAM usage was climbing by something like 100mb every 5 seconds, and this would continue until Skate was consuming upwards of 20-25gb RAM, and eventually the game would crash.
But when swapping the Upscaling Method from XeSS Balanced to either FSR Balanced or None, Skate's RAM usage no longer climbs, and sits at a stable number. So far this seems to be around either 4gb or 9.5gb, depending on garbage collection events.
The RAM usage continues to be just as stable even after disabling Radeon Chill and running the game at 120-140fps.
Hope this helps.