The best Game Library Manager alternative to Razer Cortex is Playnite, which is both free and Open Source. If that doesn't work for you, our users have ranked more than 10 alternatives to Razer Cortex, but unfortunately only two of them are Game Library Managers.
Open-source launcher and manager organizing PC, emulated, and custom games from platforms such as Steam, GOG, Origin, and Uplay under a single customizable interface, supporting metadata, controller mode, plugins, themes, playtime tracking, and multi-language options.
Centralized game library management service, allowing you to host games on one device and connect multiple clients, supporting cross-platform play and emulation. Easily manage emulator profiles, with web client access for metadata and artwork showcase.
Czechia
EU
Sure, they are both good at organizing games, but Razer Cortex also has a gamebooster (which was the main reason I downloaded it.) Though if you're looking for an open source game manager and launcher, this is good.