when controllable detects a controller, it takes full control of it, which, like steam, may cause issues with other programs, namely DSUClients (see #113), causing inputs to be falsely detected in both programs

Can you explain what DSU Clients are? Both Google and DuckDuckGO yield no useful results. It seems like something this mod is not designed to support.

clients that virtualize DS4s over a server but with motion controls and a touchpad (mainly used in emulators of consoles with motion controls), and can also virtualize XInput,
here are all the ones for windows:
Switch controllers - BetterJoy - https://github.com/Davidobot/BetterJoy
DualShock 4 - DS4Windows - https://github.com/Ryochan7/DS4Windows (Ryochan7's fork - original isn't updated anymore)
WiiMoteHook - https://github.com/epigramx/WiimoteHook
SteamGyroForCemuhook - https://github.com/FrogTheFrog/steam-gyro-for-cemuhook

you can also use a controller over the internet with those, due to the use of servers (by default, they are configured as IP 127.0.0.1, making them inaccessible for anyone else, but you can make them accessible to everyone on your network, or if you port forward anyone on the internet by setting IP as 0.0.0.0)

issues like this are the reason HIDGuardian exists, but it just doesn't seem to work sometimes

I'm still confused at what needs to be "fixed". Turn off auto select in the options if you don't want the controller selected automatically. DS4Windows works fine with Controllable. It sounds like a large scale issue and not directly Controllable.