Aside from GOG and itch.io there is Zoom Platform (not to be confused with Zoom), a much more obscure store selling mostly very old titles, with only a few more modern games. I found it while looking at the PCGamingWiki page for Race Driver: GRID.

Funnily enough they are the only online store that still sells that game (and with no DRM) seemingly because its publishers just... forgot that the store existed? So they never de-listed it.