I'm running it on fabric 1.19+ in the medieval Minecraft modpack.
The mod works as intended except for when I equip it I can not open the backpack even if I switch key binds.

make sure any other keybind is not linked with backpack keybind, I'm sure it works since many players play on medieval mc and they didn't report such issue

unfortunately, the problem also applies to me, version 1.19.2 2.8.2.29-30, both on the version with the ending 29 and 30, the associated key does not work

Please re-open with new debug elements:

• TravelersBackpack-1.20.1-9.1.4
• MinecraftForge v47.1.3
• Happens in Operating System Linux (might be of importance with native implementation of LWJGL JInput)
  • java version 17.0.4 by Eclipse Adoptium; OS Linux arch amd64 version 6.2.0-1009-lowlatency,
  • LWJGL version 3.3.1 build 7
• Happens with French keyboard layout
  -Whatever non-conflicting key is assigned; it cannot open the Backpack GUI.

Significant glitch:
Once Backpack GUI is open by right-clicking on the Backpack: Assigned bound key actually closes the GUI, but is unable to re-open the GUI. So, it means, the mod never receives the key event unless in GUI.