I'm not sure how teams are out there ducking BYU. As you've already pointed out, it's a non-starter for most conferences due to coronavirus rules.

The PAC-12 (being both open to it and somewhat more local) are definitely willing to work with BYU - we've already seen BYU be their top choice. The issue is that the PAC12 (as a P5) is dealing from a position of strength and can call all the shots, which BYU just isn't ok with.

BYU has always been insistent on being treated as an equal and unwilling to make concessions (witness the statements around potential Big 12 expansion a few years back), so they're not willing to take on a game that they feel the setup isn't fair to them. But other teams (like SDSU) are willing to make those sacrifices for the opportunity

That's the difference. Nobody is 'ducking' BYU. They'd like to play BYU, but any game the PAC12 plays will be by their standards. Other teams are willing to do that, BYU isn't.