How to filter giveaways by region?

You can do something like this: https://www.steamgifts.com/giveaways/search?region_restricted=true but I believe that is just strictly region restricted games not necessarily SA/AE restrited. I believe it does filter based on your region but I'm not too sure how to test this and being in Canada I think it is a fairly open region.

You probably don't want to do that. You're better off hiding giveaways for games you don't want than trying to filter it to regions.