Mouse side buttons (M4, M5) does not seem to work on PS5 with keyboard and mouse setup.
Wired keyboard: Steelseries Apex M500
Wireless mouse using dongle: Logitech G502X Lightspeed, Razer Orochi V2, Razer Basilisk X Hyperspeed
Wired mouse: Lenovo Legion M300
Side buttons M4 and M5 can’t be used to bind controls. Also tried using Logitech G Hub and Razer Synapse app to bind side buttons to keyboard commands, and saving them to onboard memory to no avail.
Wired mouse side buttons can’t be used too.