Can supernatural beings other than mages and vampires learn magic? Would others be able to learn thaumaturgy/blood magic, or is that only a vampire thing that other supernaturals cannot learn? I know that Mages can't be embraced and Vampires can't Awaken, but is there a way to even obtain at the very least minor magic, such as with a Werewolf gift?
There's a high level gift, the Irraka Milestone Gift, actually, that lets the werewolf copy a supernatural power once they've seen it. This can be anything up to and including Mastery level Awakened magic, but it's one rote per use (or that's how we ran it anyway) and it costs 5 essence and a willpower dot to use it. Once they've got it, though, they can use it repeatedly. They still have to buy the power, at 8 exp * level.
Otherwise, there are side-steps: A mage who dies and becomes a ghost (rare) retains some of their powers (their rotes, I think) as numena. A Bone Shadow or Sin Eater could likely bind the ghost to at least some limited service and get power that way.
There are also loads of ways for mortals to gain powers, e.g. Second Sight, being a Proximus (see Silver Ladder, I think) and becoming possessed/ridden.
Oh, and there are always items as a source of power, either from the other game lines (alchemical products, imbued items, artifacts, fetishes, etc.) or relics (from reliquary). Oh, and pacts. You can always make a pact with a powerful spirt, demon or other entity for abilities you shouldn't have.