This interview has some details about how it was done on Xbox: https://hanselminutes.com/632/eric-heutchy-on-backward-compatibility-xbox-one-x-enhanced-games-and-the-heutchy-method

This site has been a great source of news about all things retrogaming.
I support them on patreon now and hope they will make it through!

Some of their articles are a bit quirky, with the writing style suffering from occasional diversions which may even turn into rant or two. But I find this somewhat endearing rather than annoying. It conveys that they love doing what they’ve been doing.

I bought all the GBA FF games off eBay and only received counterfeit ones :-/ At least the ones I got don’t have batteries in them. Saving makes the games freeze for a small time but other than that they are working.

Completed the FF V GBA counterfeit on a DS lite. Ended up playing through the DS versions of III and IV, also off eBay, which do not seem to be fakes fortunately.

Give the Nier series a try. Starting with Automata is probably the best way in. The Replicant remake is great too but it might take more time to grow on you because Replicant’s opening is slow and not as captivating compared to Automata. Both are great RPGs once you get into the thick of them. Both games have several chapters (aka playthroughs but that term is misleading) which can make them quite long but enjoyable all the way. I have sunk more than 100 hours into each of them.