Xiaomi Mi Router 4A Gigabit Edition (R4AG/R4A Gigabit) -- fully supported and flashable with OpenWRTInvasion

[Double-G]

Problem does not occur on TL-WPA8630Pv1 which is QCA-based running 21.02.0RC4, so the problem seems to be MT7xxx related.
Maybe it is due to the lack of igmp-snopping support in hardware of the MT7530-switch? See (1) and (2)]