Hey All, some of you may know this one but I just discovered it (from a 5 year post that came up on a google search for free zbrush alternatives from u/BillieRubenCamGirl )

https://stephaneginier.com/sculptgl/

an in browser clay like sculpting tool. Looks great and the dev has made a ios and android version that looks more feature complete https://nomadsculpt.com/

Amazed with it and I will def be using it