I can’t say for Lollypop. It seems quite fast, but I haven’t used it too much to really tell. Also still a bit buggy. Rhythmbox can handle large collections. It’s for sure not the most fancy and modern player out there, but it is feature rich and stable (first code dates back 2002) and still gets frequent development activity, even though it is clearly in maintencance mode (bugfixes mostly).
For quodlibet maybe, see this feature request. I didn’t know gmusicbrowser. It shouldn’t bee too hard to adapt the existing audioscobbler plugin for the ListenBrainz API, but I will definitely not work on this (because of time and Perl).
If you just want a quick hack to use ListenBrainz with gmusicbrowser, edit the audioscrobbler.pm plugin file and replace http://post.audioscrobbler.com with http://proxy.listenbrainz.org in gmusicbrowser/plugins/audioscrobbler.pm at master · squentin/gmusicbrowser · GitHub . Then set your MusicBrainz username as the user and the ListenBrainz user token as password in the plugin settings. This will use the Last.fm compatibility API of ListenBrainz. I did not test this, but give it a try 