Modern epoxies often claim to be UV stabilized, and as far as I can tell, this is a relatively recent advancement. For reference, I used Entropy CCR (slow cure) for the final model: https://entropyresins.com/product/ccr-clear-casting-epoxy/
We had UV-stabilized resins for the past two decades or so, but it just slows down the process. I used several UV-stabilized products and it just doesn't last.
For the UV-stable options, you have polyesters (which are very smelly) and premium aliphatic polyurethanes (which are finicky to work with).
For the UV-stable options, you have polyesters (which are very smelly) and premium aliphatic polyurethanes (which are finicky to work with).