The Jupiter 6 and a later model of the prophet were pretty much the first, the DX7 came quickly thereafter.
The keyboard player in our band back then had a Prophet 5 series 1, it was amazing at the time, but had major problems with overheating, which pretty much screwed it for gigs. We actually got in communication with Dave Smith and had it sent down for repair, but it didn’t help much, I added a large heat sink to it but the problems persisted and he eventually got rid of it.
The DX7 was the first MIDI capable synth we got.