I reproduced the problem again and am attaching a new failure-time
capture.

The affected kernel for this occurrence was:

7.0.0-28-generic

Attached files:

failure-Jul23.zip: complete failure-time diagnostic archive containing the full 
Wi-Fi debug report, and containing these files:
$ sudo dmesg > dmesg_Jul23_239pm 

$ sudo journalctl -k -b > kernel-journal.txt

$ sudo journalctl -u NetworkManager -b > ~/NetworkManager-journal.txt

$ iw dev > ~/iw-dev-failure.txt

$ sudo journalctl -u wpa_supplicant -b -1 > ~/wpa_supplicant-Jul23.txt

In this occurrence, both GNOME and:

nmcli dev wifi list

showed no available Wi-Fi networks. The USB device and wireless phy were
still present, and rfkill was not blocked.

The logs show repeated network disconnections with reason 252 at
approximately four-hour intervals. Earlier events recovered normally.
For example, the 03:06:47 disconnect was followed by successful
reconnection at 03:06:51 and another successful association at 03:07:39.

wpa_supplicant continued producing normal signal-change messages until
05:42:04. After that, it produced no further messages for more than nine
hours.

The kernel later recorded another disassociation, but NetworkManager
continued to retain stale activated connection state even though the
interface was no longer associated.

A new scan request eventually failed with:

request-scan: could not get scan request result: Timeout was reached

After toggling Wi-Fi off and back on, NetworkManager repeatedly failed
to recreate the supplicant interface:

Couldn't initialize supplicant interface: Timeout was reached

and eventually reported:

supplicant interface keeps failing, giving up

During shutdown/recovery, wpa_supplicant could not process SIGINT or
SIGTERM and reported:

eloop: could not process SIGINT or SIGTERM in two seconds.
Looks like there is a bug that ends up in a busy loop that
prevents clean shutdown. Killing program forcefully.

This occurrence did not produce the previously observed:

unregister_netdevice ... Usage count = 2

teardown deadlock, because I did not attempt USB unbind this time.

This appears to be a reproducible failure where wpa_supplicant or an
underlying nl80211/driver operation becomes nonresponsive, preventing
scans and reconnection. It is not yet clear whether this is a precursor
to the previously reported mt7921u teardown deadlock or a separate
issue.

Please advise whether wpasupplicant should be added as another affected
package/task, and whether any additional targeted tracing should be
enabled before the next occurrence.

I am willing to test the suggested 7.2-rc4 mainline kernel and any
instrumented kernels or proposed patches.

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https://bugs.launchpad.net/bugs/2161448

Title:
  mt7921u: USB Wi-Fi enters unrecoverable state after prolonged uptime;
  NetworkManager/supplicant stalls followed by USB disconnect deadlock

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