According to this site, Sinclair released a total of ten titles on cartridge: all games that were popular on cassette, and all in 1983, the year the Interface 2 was released.
I know the cartridges flopped pretty quickly, largely because most Spectrum users weren't willing to pay thrice the price of a cassette just for an instant load. Still, Sinclair promoted them in the Spectrum+ manual (1984) and, per this q, there were third-party cartridge interfaces in the wild around that time.
Did any other company release Spectrum software on cartridge? If so, how many titles in total were released?
I'm particularly looking for releases while the Speccy games market was still current, so before 1995 (I think that's a fair cut-off), but I'll also accept later commercial offerings for the clone market(s), or a reliable source saying no such cartridges were made.