I just migrate from 19.08 to 21.02.2 on my wrt1900acs.
Watching tv channel through with VLC is OK.
But getting the same tv channel via apple tv does not work if i select IGMP snooping on the device.(br-lan)
If i do not select IGMP Snooping i can get tv channel from VLC and apple tv but there is a lot of traffic who block the wifi and its impossible to access internet. I have to stop watching tv and wait few minutes before the network is available.
This is something that did not happened with 19.08. IGMP snooping was selected and its worked on apple tv.