Steam
GOG
Microsoft Store (and now Gamepass and the XBOX app)
Origin
UPlay, I guess...
EGS
Steam and GOG are where my biggest libraries are. Microsoft Store because of the handful of XBone games that came to PC. Origin because of the half dozen EA games I give a shit about, and EGS is still only populated by free games. Though I will have no issues buying a game on there if the price is the lowest.