GUI-configurable systemd mount for firmware directory in Homeassistant OS

[supergonzo74]

Background & Issue

Running Homeassistant OS 2025.5.3 on a Proxmox Hypervisor as VM I came across an issue that after successfully passing-through my bluetooth-dongle the hardware was recognized but due to missing firmware in /lib/firmware failed to initialize.

Struggling with this issue and searching the internet for days now it turns out that no only me but lots of others have problems with failing hardware initialization due to the lack of third-party firmware under "/lib/firmware". On Homeassistant OS VM installations unlike on other plattforms you couldn't even just append "firmware_class.path" from vm-config as this only works in conjunction with "-kernel"-directive which in turn expects a real filesystem path instead of a grub-like notation like i.e. in my case (hd0,gpt2)/bzImage.
Also trying to mount-shadow the empty "/lib/firmware" directory from a custom automation via "shell_command" fails as the mount ends up to be in "homeassistant" container instead of the host-VM as "automations" seem to be carried out by this one. So in this environment we seem to be completely out of luck...

Proposed Solution

Introduce the ability to mount-shadowing "/lib/firmware" directory via systemd mount at early boot so that the firmware can be made available to the host-VM, similar to how "media", "backup", and "share" are handled under "Settings->System->Storage->Add Network Storage":

This feature should:

Provide a GUI-based systemd mount manager (like for the hardcoded paths/types above), allowing users to mount over existing but empty "/lib/firmware" directory of the host-VM.

Benefits

• Enables Bluetooth dongles, Wi-Fi adapters, and custom hardware to function correctly on Homeassistant OS.
• Improves support for virtualized environments like Proxmox, where firmware needs to be injected at boot.
• Reduces manual workarounds (SSH access, temporary mounts) that get wiped after a restart.

Hints

Due to that fact that this mountpoint needs to be available relatively early at boot the unit from my point of view needs to be available before udevd "finds" the hardware

Community Interest & Feasibility

Given the number of users facing firmware issues with virtualized Homeassistant OS installations, this feature could significantly enhance hardware compatibility and virtual machine usability. Since Homeassistant OS already allows systemd mounts for certain directories, extending this functionality to firmware storage should be feasible within the existing architecture.