Franz, Rambox, Ferdi (defunct I think) and so on. Been but a few posts about these.
I'm currently trying Ferdium https://github.com/ferdium/ferdium-app, which seems to be successor to Ferdi, which itself was a variant on Franz (which has paid options added).
I have been using Whatsdesk and also Whatsapp desktop electron apps as frontend to Whatsapp Web, since once phone logs you in via QR code scan, you can switch phone off and not need it to log in again apparently (unlike whatsapp web itself which needed QR code scanned in next time used again - also needs phone left on I think whereas these electron-based apps don't require that, it seems, though how I don't know, but: it is a big advantage).
Well both Whatsdesk and Whatsapp Desktop for Linux work well from my needs (which I have), but so it seems does Ferdium (did for Whatsapp anyway), and with ability to use many other such web messaging services. My experiments with Ferdium continue.