I think we misinterpreted each other.
In my original comment, I mentioned two separated cases. First, a “some ROMs”, referencing a more general landscape, and then the Genesis/MD collection from Sega specifically. And the “reasonably obtained” part is because some editions are very hard to come by, may be very expensive, and/or may be a nightmare to have the ROMs extracted from.
Then, with your reply, I thought you were asking about the former, when, going by my following reply, it would seem you were asking about the latter and that you thought I was talking about the latter too.
Would that be the case?
Afaik, Termux is an actual Linux system made for Android’s file system and that runs inside an app, so it actually can do a whole lot more, provided there’s a tool ported for what you want. It can even run some graphical distros.