Yay! Other than the fact that it posted twice, it worked. Probably because I clicked "Proceed" instead of "Get" on the redirect for the first time, which probably submitted it twice. My bad.
Using old.lemmy is really quick on my Thinkpad T480 (approx. 5 years old). I'm running OpenBSD; Javascript performance is pretty bad and makes the fans spin up.
I'm in Indonesia at the moment so preventing any excess heat is paramount ;)