Code Quality
Don't convert TaikoModRandom to/from legacy mods (#25823 by @cl8n)
Gameplay (osu!)
Fix slider's sliding sample playing before start time (#25893 by @smoogipoo)
Online
Update packages for mod settings changes (ppy/osu-server-spectator#205 by @peppy)
Stop tracking build user counts when shutting down (ppy/osu-server-spectator#206 by @bdach)
Performance
Improve song select smoothness when running background processing (#25838 by @peppy)
Fix some beatmaps being reprocessed each startup (#25895 by @peppy)
Song Select
Fix incorrect ordering of items at song select when certain sort modes are used (#25888 by @peppy)
This is quite an unfortunate one, but I can't see a good way of fixing beyond undoing most of the performance gains from the last major release when certain sort modes (like difficulty sort) are used.
If you have a large library and want best search performance, use a simple sort mode for now (ie. artist or title). We'll iterate on this once things calm down.
Fix mod search textbox having focus while settings are visible (#25857 by @peppy)
UI
Fix opening log files from notification not presenting the correct file (#25871 by @Susko3)
Full Changelog: 2023.1218.1...2023.1220.0