It looks like in at least one case, international theatrical subtitles made it onto a Laserdisc release (French ROTJ). I doubt this would have happened for Star Wars, but it’s possible it may have happened for one of the international laserdisc releases for which we don’t have a theatrical subtitle reference for ROTJ.

So if anyone happens to have a Spanish or Japanese laserdisc of ROTJ, I’d be interested to know what the alien subtitles look like. For Spanish, I imagine the subtitles will be approximately the same font/style as the English subtitles. For Japanese, I have no idea. If it turns out to be theatrical, I’d like a screencap of each subtitle. You could try Star Wars too, but I’m thinking 16mm prints are our best bet there.