Comment 3 for bug 1951586

>Since cloud-init's network v2 support is just straight pass-through to netplan, there doesn't seem
>to be anything for cloud-init to do here.

I tagged cloud-init just in case, as I was already expecting it to turn it into a discussion whether this belongs in Netplan, or is more a global localization like setting.

Using a post-install script to patch /etc/default/crda is problematic, because post-install scripts are executed so late.
Also does not seem to work with write_files in practice (not sure why, thought that did was executed early).
And since different operating systems put the setting in different files, some abstraction instead of OS specific commands would be preferable anyway.

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>The regulatory domain is a global concept that is being handled in the kernel and affects all radio
>devices, like WiFi and Bluetooth.

Are you sure it is the kernel that is treating this as a global thing, and not just your implementation?

Other distributions (like RPI OS) set the country in wpa_supplicant.conf instead of your /etc/default/crda, and think you can have a different wpa_supplicant.conf per adapter.
And "iw reg get" also shows it per adapter (phy) in addition to global.

BTW on the Ubuntu 21.10 aarch64 Pi image it always seems to show as UNSET even if I do set /etc/default/crda and reboot, which may be another bug.

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max@ubuntupi:~$ cat /etc/default/crda
# Set REGDOMAIN to a ISO/IEC 3166-1 alpha2 country code so that iw(8) may set
# the initial regulatory domain setting for IEEE 802.11 devices which operate
# on this system.
#
# Governments assert the right to regulate usage of radio spectrum within
# their respective territories so make sure you select a ISO/IEC 3166-1 alpha2
# country code suitable for your location or you may infringe on local
# legislature. See `/usr/share/zoneinfo/zone.tab' for a table of timezone
# descriptions containing ISO/IEC 3166-1 alpha2 country codes.

REGDOMAIN=GB
max@ubuntupi:~$ iw reg get
global
country 00: DFS-UNSET
        (2402 - 2472 @ 40), (N/A, 20), (N/A)
        (2457 - 2482 @ 20), (N/A, 20), (N/A), AUTO-BW, PASSIVE-SCAN
        (2474 - 2494 @ 20), (N/A, 20), (N/A), NO-OFDM, PASSIVE-SCAN
        (5170 - 5250 @ 80), (N/A, 20), (N/A), AUTO-BW, PASSIVE-SCAN
        (5250 - 5330 @ 80), (N/A, 20), (0 ms), DFS, AUTO-BW, PASSIVE-SCAN
        (5490 - 5730 @ 160), (N/A, 20), (0 ms), DFS, PASSIVE-SCAN
        (5735 - 5835 @ 80), (N/A, 20), (N/A), PASSIVE-SCAN
        (57240 - 63720 @ 2160), (N/A, 0), (N/A)

phy#0
country 99: DFS-UNSET
        (2402 - 2482 @ 40), (6, 20), (N/A)
        (2474 - 2494 @ 20), (6, 20), (N/A)
        (5140 - 5360 @ 160), (6, 20), (N/A)
        (5460 - 5860 @ 160), (6, 20), (N/A)

==