If you're playing a devout pc/priest, you could possibly have them undergo some sort of "cleansing" ritual to purge the evil from their soul. (Even if it fails, and they just lie.)
Interrogate and offer the chance at freedom if they agree to work as a double agent. (Again, they can still lie! Or this might even permit an evil to neutral aligned arc.)
Use them as bait/leverage for a prisoner exchange. Maybe there's a slave in the UD you want to free, and if this high ranking member is returned unharmed, someone of your choice gets returned as well.
Or maybe it's just used as a way to force a meeting in a location of your choice.
One of the initial options was curses too, and I don't see why this isn't a valid option? Obviously you would have to flavor it differently, but I don't see why you couldn't do this. There's even precedent in one of the games, if you're looking for an idea of where to start. https://torment.fandom.com/wiki/Fhjull_Forked-Tongue
Blood sports can just be re-flavored as trial by combat. Especially if it's a spectacle with a cleric of a good/lawful deity presiding over it. If players are calling your character evil for doing so, who cares...? There are a million different good aligned actions you can take that will have other characters screeching this.
In terms of long term capture, I can't really see this being done on monsters at all.
However, for petty criminals/human animators, warlocks, ect, I'm sure you could introduce a concept of a 're-education' camp or 'reform' program. Possibly with an entire group/faction committed to it.
Have them go on pilgrimages, under a tutor. Teach them the error of their ways. And sure, this could also include the resource gathering/monster slaying that was initially suggested.
I don't really think you need mechanics for this. Any sort of capture style RP is already opt in by the losing party. It's your job now to impress them to stick around.
Looking at all the counterpoints or alternative options in the UD/evil aligned places, I don't really see a big distinction. All of those require ooc consent regardless.
The only thing I could think of that would work would require significant mechanical overhauls. But, having some sort of penal colony that evil characters can be jailed to would be interesting. Prisoner island or something, where you could either do some quests to work off your time, or plot with other players to escape.