Three community Proton builds landed at the same time: GE-Proton 11-10, Proton-CachyOS 11.0-20261014 and DWProton 11.0-15. GamingOnLinux rounded them all up, and the GE-Proton release has the fix most handheld players will care about.
Since GE-Proton11-8, the automatic PlayStation controller XInput fallback rescanned every HID device each time a game polled an empty controller slot. That caused large slowdowns, even with no controller connected. Path of Exile ran at around 50 FPS instead of 200+, and Le Mans Ultimate had slow-motion physics with a Moza wheel. GE-Proton 11-10 stops the rescanning. Setting PROTON_SONY_AUTO_XINPUT=0 confirmed the cause, but the release notes say the fix itself hasn't been confirmed in-game yet.
GE-Proton 11-10 also gets Bluetooth DualShock 4 and DualSense rumble working through the XInput fallback, so input no longer stops after the first rumble, and it pulls in a newer Valve bleeding-edge Wine and DXVK v3.1.1-134.
Proton-CachyOS moves to Proton Experimental 11.0-20261014 with fixes for Arknights: Endfield, Loop Hero crashing with WOW64, Warcraft III and Warhammer 40,000: Space Marine 2. Its native-only build adds partial, work-in-progress 32-bit PhysX support on AMD through ZLUDA, though that native build doesn't currently work with Steam since the client moved to SteamRT3. DWProton 11.0-15 updates to the new CachyOS base.
My take: If you're on GE-Proton 11-8 or 11-9 on a Steam Deck or another SteamOS handheld and a game has felt slower than it should, 11-10 is worth trying. Since the fix isn't confirmed in-game yet, I'd keep an older GE-Proton or Valve's own Proton installed as a fallback.