Sega are having a sale on Steam currently, with their “Sega Genesis and Megadrive Classics Collection” getting a 90% discount, and coming it at under $10: https://store.steampowered.com/app/34270/SEGA_Mega_Drive_and_Genesis_Classics/
Included are 58 games. Sega provide an interesting “virtual room” experience with a TV and shelves showing off the games (including VR mode which is kind of cool), however what’s more useful is that most of the games are merely uncompressed, legal ROMs in your Steam folder on-disk.
You can rename these yourself (just add a “.md” file extension), or run Smokemonster’s Everdrive rename tools over them:
https://github.com/SmokeMonsterPacks/EverDrive-Packs-Lists-Database
From here, the games can be copied to a Flash Cart, loaded in an emulator of your choice, or run on FPGA systems like MiSTer or the Analogue Mega Sg.
A quick test in RetroArch shows many of these working well. This is a great way to grab a bunch of legally purchased ROMs for a low price.