Where do you usually purchase pc games from? Pick up to 2 options/ most common practices for your case.
Share the reason why you support that specific platform.
Steam mostly. The Steam UI is about the only service that offers a good UI for large libraries IMO. Epic games isn't a bad platform, but the UI looks like it wants to be a mobile store and that just doesn't work well if I were to add 100s of games to it. GOG is not bad, but the whole having to go through menus to play some expansion DLC and a lot of other little things just don't sit well with me.
I used some Steam from gift keys and both Epic for Dauntless (but I never used but free games are nice) and itch for random interests. But I don't really care because I don't really want to use my laptop for high spec gaming.
I used Steam and that other site called Zoom Platform, which is another Retro and Modern PC Game Site, I owned all the Duke Nukem Games from Zoom Platform, and played them on my laptop, I feel Proud of myself.