@Kevin,

Thank you for testing again. This latest output indicates something may not be correct in your test environment. This line:

WARNING:root:_pkg_get_support nvidia-driver-525: package has invalid Support PBheader, cannot determine support level

is indicating that the driver packages are providing a "PB" in the support field, but ubuntu-drivers doesn't know how to handle this. Support for PB drivers was added in version 1:0.9.0~0.20.04.7, which is the latest version in focal-updates (see lp:1964747 for details). This indicates this particular test was run with an even older version, but that doesn't make sense if you've also updated to 1:0.9.0~0.20.04.8. I really can only speculate what is going on here.

I did run an experiment on a device attached to testflinger, 202007-28059. This is an HP ZBook Studio G7 with a TU117GLM [Quadro T2000 Mobile / Max-Q]. This appears to match the devices used in the original bug description. I first verified that the problem exists with the version of the package in focal-updates:

ubuntu@hp-zbook-studio-g7-c28059:~$ dpkg -l|grep ubuntu-drivers
ii  ubuntu-drivers-common                 1:0.9.0~0.20.04.7                 amd64        Detect and install additional Ubuntu driver packages
ubuntu@hp-zbook-studio-g7-c28059:~$ sudo ubuntu-drivers devices
ERROR:root:could not open aplay -l
Traceback (most recent call last):
  File "/usr/share/ubuntu-drivers-common/detect/sl-modem.py", line 35, in detect
    aplay = subprocess.Popen(
  File "/usr/lib/python3.8/subprocess.py", line 858, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/usr/lib/python3.8/subprocess.py", line 1704, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'aplay'
== /sys/devices/pci0000:00/0000:00:1f.4 ==
modalias : pci:v00008086d000006A3sv0000103Csd00008736bc0Csc05i00
vendor   : Intel Corporation
driver   : oem-stella.cmit-meowth-meta - distro free

== /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0 ==
modalias : pci:v000010DEd00001FB8sv0000103Csd00008736bc03sc00i00
vendor   : NVIDIA Corporation
model    : TU117GLM [Quadro T2000 Mobile / Max-Q]
driver   : nvidia-driver-535-server - distro non-free
driver   : nvidia-driver-535-server-open - distro non-free recommended
driver   : nvidia-driver-535 - distro non-free
driver   : nvidia-driver-525-open - distro non-free
driver   : nvidia-driver-535-open - distro non-free
driver   : nvidia-driver-450-server - distro non-free
driver   : nvidia-driver-470 - distro non-free
driver   : nvidia-driver-418-server - distro non-free
driver   : nvidia-driver-525 - distro non-free
driver   : nvidia-driver-470-server - distro non-free
driver   : nvidia-driver-525-server - distro non-free
driver   : xserver-xorg-video-nouveau - distro free builtin

Then updated to the package from proposed:

ubuntu@hp-zbook-studio-g7-c28059:~$ dpkg -l|grep ubuntu-drivers
ii  ubuntu-drivers-common                 1:0.9.0~0.20.04.8                 amd64        Detect and install additional Ubuntu driver packages
ubuntu@hp-zbook-studio-g7-c28059:~$ sudo ubuntu-drivers devices
ERROR:root:could not open aplay -l
Traceback (most recent call last):
  File "/usr/share/ubuntu-drivers-common/detect/sl-modem.py", line 35, in detect
    aplay = subprocess.Popen(
  File "/usr/lib/python3.8/subprocess.py", line 858, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/usr/lib/python3.8/subprocess.py", line 1704, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'aplay'
== /sys/devices/pci0000:00/0000:00:1f.4 ==
modalias : pci:v00008086d000006A3sv0000103Csd00008736bc0Csc05i00
vendor   : Intel Corporation
driver   : oem-stella.cmit-meowth-meta - distro free

== /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0 ==
modalias : pci:v000010DEd00001FB8sv0000103Csd00008736bc03sc00i00
vendor   : NVIDIA Corporation
model    : TU117GLM [Quadro T2000 Mobile / Max-Q]
driver   : nvidia-driver-535-open - distro non-free
driver   : nvidia-driver-525-open - distro non-free
driver   : nvidia-driver-450-server - distro non-free
driver   : nvidia-driver-535-server-open - distro non-free
driver   : nvidia-driver-535 - distro non-free recommended
driver   : nvidia-driver-418-server - distro non-free
driver   : nvidia-driver-470-server - distro non-free
driver   : nvidia-driver-535-server - distro non-free
driver   : nvidia-driver-525-server - distro non-free
driver   : nvidia-driver-470 - distro non-free
driver   : nvidia-driver-525 - distro non-free
driver   : xserver-xorg-video-nouveau - distro free builtin


Based on this, it is now choosing the expected `nvidia-driver-535` driver.

I can look further, but I'm going to need to triage the problem on your test device or somewhere you can reproduced this.