light-locker disconnects the bluetooth devices when locking.

This is just a screen locker. Locking should not affect bluetooth.

If this issue is about Bluetooth *sound* disconnecting on locking, I
believe this is likely an undesired interaction between light-locker's
VT-switching for integration with lightdm [1] and per-user Wireplumber's
disconnecting Bluetooth on VT-switches (unless both VTs are owned by the
same user) [2].

[1] https://github.com/the-cavalry/light-locker/blob/master/README.md
[2]
https://pipewire.pages.freedesktop.org/wireplumber/daemon/configuration/bluetooth.html

I don't have great ideas for a platform/code-level fix, but felt some
information on the mechanism might be useful here.

Thanks, yes, this is about audio devices. I'll have to try.
If the

wireplumber.profiles = {
  main = {
    monitor.bluez.seat-monitoring = disabled
  }
}

documented in [2] avoids sound disconnecting, this would be OK for
me, I think (with the benefit that this would also avoid the same
issue with other kind of VT switching, which I have not tried).
In such a case, I think that this should be documented in the
light-locker man page.