Don't know if this fits since it's a new game for a retro console, but as a big collector of retro handheld stuff this has been a treat!
The Machne is a muti-ending RPG for the GBC where you play as GIRT, a denizen of The Machine.
It's seriously great, I've probably seen 10 endings so far and I've only just figured out how to ditch my factory job and live as an artist. I've killed people, moved drugs, sorted boxes, been rich, been homeless, rigged elections -- there's something for everyone.
They released both a physical cartridge and a ROM version that includes a .pocket file if you're rocking an analogue. Available here!
There's also a demo on itch.io
(Feel free to remove if this doesn't fit in retrogames!)
I'd love to get some reommendations for any other titles you've enjoyed in this space (new game / old platform)
The other one off the top of my head that I've personally tried is Deadeus which was kinda the poster child for GBStudio.
I also really enjoyed Super Jacked Up Tomato Face Johnson, which is much simpler but stays fun.