Can confirm: this is an incredibly low-barrier-to-entry thing.

I'm a U.S. citizen, so I signed up with Be The Match. Four cheek swabs that they send you in the mail. Swab your cheeks, package them up, send them back.

I got notified that I was a preliminary match just five months after signing up. Sadly, I wasn't a full match (hopefully someone else was!) after going through the blood draw.

All in all, it cost me nothing monetarily and maybe 3 hours total between questionnaires and the blood draw when I got matched.