FYI: Retrode2 was able to read the game ROM from Sega Mega-Tech Tetris. The game ROM contents are bit-for-bit identical to those of the barely-released (recalled?) Japanese Mega Drive Tetris cartridge.
Sega Mega-Tech cartridges appear physically identical to Japanese Mega Drive cartridges but with a partly different pinout (they apparently have a second ROM for the second screen and side B of the cartridge is wired differently from Mega Drive) and much less exciting labels, and are intended for use inside a Mega Drive-like arcade machine with extra hardware for coin mechanisms, instructions display, etc.
Somehow Retrode2 can read the game ROM though, so this allows use of the original cartridge's game data in an emulator-based modern system.
Thanks yet again for the awesome hardware and firmware!
P.S. Maybe someone knows a way to dump the extra ROM for the second screen? The pinout is at least mostly known
https://assemblergames.com/threads/sega-mega-tech-adapter.45818/
https://segaretro.org/Mega-Tech_System
https://wiki.arcadeotaku.com/w/Sega_Mega-Tech
https://segaretro.org/Tetris
The second monitor program runs on a Master System derivative. Any idea whether it's possible to read that using the Retrode2 without an adapter?