I tried to Give Major Rhymer Advanced Proton Torpedoes in the squad builder app and on YASB but it is unavailable to him. Looking at the torpedo card, I see no requirement except that it is a torpedo, which Tie Bombers (which Rhymer is a bomber) can equip. So, why are advanced proton torpedoes not available to him?

Well, they aren’t available in Hyperspace, only Extended, ugh!

It doesn't look like they're available for Hyperspace.

YASB *would* let me put them on Rhymer in Extended.

Official Generic Upgrade list

https://images-cdn.fantasyflightgames.com/filer_public/8c/35/8c35b582-2af1-44a7-927d-6e0d64b778d5/onlinepoints_resistance_january.pdf

Here's the correct link:

https://images-cdn.fantasyflightgames.com/filer_public/3f/31/3f314ee6-b962-419f-9149-9daec4ce3747/onlinepoints_genericupgrades_wave3.pdf