upsdrvctl start no longer works (insufficient permissions on everything)

[myyc]

i've seen this reported elsewhere (e.g. #1983). in my case it plainly stopped working, but i don't know when.

briefly:

• using debian stable (upgraded to sid's 2.8.1 to see if that'd change anything)
• the ups works
• it gets recognised by lsusb (Bus 002 Device 005: ID 0764:0501 Cyber Power System, Inc. CP1500 AVR UPS)
• nut-scanner works as root
• permissions are fine in all relevant paths (/run/nut, etc.)
• /lib/nut/usbhid-ups -a ups -DD fails with the following

   0.000028     [D1] debug level is '2'                                                                                                              
   0.000233     [D1] Succeeded to become_user(nut): now UID=123 GID=133                                                                              
   0.000252     [D1] upsdrv_initups (non-SHUT)...                                                                                                    
   0.000260     [D2] Initializing an USB-connected UPS with library libusb-1.0.26 (API: 0x100010a) (NUT subdriver name='USB communication driver (lib
usb 1.0)' ver='0.46')                                                                                                                                
   ...
   0.009685     [D2] Checking device 10 of 11 (0764/0501)
   0.009695     [D1] Failed to open device (0764/0501), skipping: Access denied (insufficient permissions)
   ...
   0.009719     [D2] libusb1: No appropriate HID device found
   0.009725     libusb1: Could not open any HID devices: insufficient permissions on everything