Comment 3 for bug 2049220

Loaded the firmware files from the commits listed in the Bug Description into my system and I can confirm it also fixes the issues on the 6.5 HWE Kernel (6.5.0-14-generic). This restores IPv6 connectivity for this WiFi device (depends on Multicast for things such as RA's/ND's).

fludizz@pauwel:~$ uname -a
Linux pauwel 6.5.0-14-generic #14~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Mon Nov 20 18:15:30 UTC 2 x86_64 x86_64 x86_64 GNU/Linux

fludizz@pauwel:~$ sudo dmesg | grep mt7921
[ 9.026969] mt7921e 0000:05:00.0: enabling device (0000 -> 0002)
[ 9.034524] mt7921e 0000:05:00.0: ASIC revision: 79610010
[ 9.120620] mt7921e 0000:05:00.0: HW/SW Version: 0x8a108a10, Build Time: 20231109190918a
[ 9.132797] mt7921e 0000:05:00.0: WM Firmware Version: ____010000, Build Time: 20231109190959
[ 9.964058] mt7921e 0000:05:00.0 wlp5s0: renamed from wlan0

fludizz@pauwel:~$ ip -6 addr show wlp5s0
3: wlp5s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    inet6 2a10:3781:3fbd:xxxx:xxxx:xxxx:xxxx:xxxx/64 scope global temporary dynamic
       valid_lft 86394sec preferred_lft 14394sec
    inet6 2a10:3781:3fbd:xxxx:xxxx:xxxx:xxxx:xxxx/64 scope global dynamic mngtmpaddr noprefixroute
       valid_lft 86394sec preferred_lft 14394sec
    inet6 fe80::xxxx:xxxx:xxxx:xxxx/64 scope link noprefixroute
       valid_lft forever preferred_lft forever

fludizz@pauwel:~$ ip -6 route | grep ra
2a10:3781:3fbd::/64 dev wlp5s0 proto ra metric 600 pref medium
default via fe80::xxxx:xxxx:xxxx:xxxx dev wlp5s0 proto ra metric 600 pref medium

However, this firmware did introduce a new warning in my logs, which was not present with the previous firmware (regardless of kernel version):
[ 101.523786] warning: `ThreadPoolForeg' uses wireless extensions which will stop working for Wi-Fi 7 hardware; use nl80211

So keep this in mind when using the updated firmware. The MT7921 is a WiFi6 device so I do not expect it to be affected by above warning.