Cool DX7 patch generator for hard and software (Dexed, FM8…)
Lots of free DX7 sysex files from Bobby Blues to use in hard and software (Dexed, Fm8…)
Native Instruments offer a ton of sounds (2000) and instruments (Synths, Smaples Instruments) plus an organizer app (Komplete Kontrol) for free. Download here.
Zombi-Fights-Shark compiled 60000 presets from Yamaha DX sysex files for Native Instruments FM8 VST synth. You can download these for free (Donation possible).
Get a couple of free (Mostly Synthwave) patches for diverse synths like Serum, U-no-LX, PG-8X and more at The Patchbay.