https://ares-emu.net/
I've stumbled on Ares recently, when looking for a good N64 emulator, and it seems to be a pretty nifty multi-system emu. Think Retroarch but without the bloat. Of course it also means it misses some functionality, but is an interesting alternative nonetheless.
I saw they also added Sinclair as "exeprimental". Has anybody tried this yet? It seems pretty bare bones and I couldn't really do anything, but it is said to emulate Kempston, plus tzx/tap, so some games should be playable.