There are a couple releases distributed on actual ROM cartridges compatible with existing systems. Plus a bunch of gamerips which should probably use this format too instead of digital media.

• https://musicbrainz.org/collection/bd923633-35e2-4363-85d9-fc0090e2d071
• https://en.wikipedia.org/wiki/ROM_cartridge
• https://musicbrainz.org/search?query=comment%3A%28gamerip%7C%7C%22game+rip%22%29&type=release&limit=100&method=advanced

The unknown ones previously were incorrectly set to cartridge which is actually magnetic tape.