I looked up my other libraries / PC launchers, too.
Steam: 5158 (+358)
GOG: 549 (+85) ... my library shows 575, but that includes demos and goodies
Epic Games Store: 582 (+91)
Prime Gaming (Launcher): 532 (+57)
Electronic Arts: 95 (+0 ... last game bought 2022)
Ubisoft Connect: 89 (+0 ... last game bought 2021)
Meta Store: 51 (+0 ... last game bought 2020)
Legacy Games: 38 (via Prime Gaming)
Battle.net: 8 (+0 ... last game bought 2022)
Rockstar Social Club: 8 (+0 ... last game bought 2021)
Windows Store: 7 (+0 ... last game bought 2022)
Itch.io: 1000+ (mostly free games or from their charity bundles)