I have been gaming since 1992 and building PCs since 2003. I enjoy Linux, supporting FOSS projects and am a tinfoil hat connoisseur.
I use KeePassXC which doesn’t charge a cent for this.
I don’t know if Firefox’s is safe but I use and love KeePassXC:
One of the reasons I prefer GOG is that I don’t want to use a client. I prefer to download offline installers and then run my games through Lutris or Heroic Games Launcher.