Comment 8 for bug 1991725

To workaround the issue by rebuilding and signing the driver manually:

1: Run "sudo dpkg-reconfigure bcmwl-kernel-source" to rebuild the driver.
2: Run "sudo kmodsign sha512 /var/lib/shim-signed/mok/MOK.priv /var/lib/shim-signed/mok/MOK.der /lib/modules/5.19.0-21-generic/updated/dkms/wl.ko" to sign the driver.
3: Run "sudo modprobe wl" to load the driver. At this point the WiFi module should start working and you should be able to connect to WiFi.

Note that this assumes that the wl.ko module is at /lib/modules/5.19.0-21-generic/updated/dkms/wl.ko, however since the user probably hasn't managed to update their kernel yet, it's a safe bet that this is in fact where the module is.