I had the same problem.
As a workaround I installed and enabled udpxy
and disabled igmpproxy
.
I then manually activated/added the IGMP rules in the firewall:
config rule
option name 'Allow-IGMP'
option src 'wan'
option proto 'igmp'
option family 'ipv4'
option target 'ACCEPT'
option enabled '1'
config rule
option name 'Allow-Multicast'
option src 'wan'
option proto 'udp'
option family 'ipv4'
option dest_ip '224.0.0.0/4'
option target 'ACCEPT'
option enabled '1'
I was lucky, since I use with “IPTV Simple Client” on KODI. It has is an option to add the IP address of your udpxy
server, and that’s all it needs.