You can already use Sketchup for UV unwrapping. It’s still a bit behind other Software in terms of features (no support for ngons, no atlases, no UDIM, no second UV space…), but it works very well:
So, I guess Twinmotion might be a very nice path for architecture and environments into UE, but for objects, vehicles and entourage you can already develop them with Sketchup and Wrap-R. The