Hey there @ebiebi405! Welcome back to the community! Every Quixel asset that made it’s way to Fab is under the Fab Standard license, so those are covered for any engine. Legacy Quixel assets under Quixel’s platform are available for free under the indie license for all engines up to $2m in revenue but you have to claim it before December 31, 2024.
Correct, you should claim all on both Fab’s claim page and Quixel’s legacy claim page so that you can retain access to everything when the Quixel assets become unavailable or change license if they are updated. Everything on the Quixel side under the indie license and everything on Fab under the Fab standard license.