For some odd reason, I never experienced any problems with JRiver Media Center 28.0.100 or 28.0.103 64-bit for Intel-based Macs yet with regard to IPTV. I updated to the current release version and restarted it and tested IPTV and I was able to tune into American, Swiss, and Chinese television stations, channels, and networks mostly just fine; however, my IPTVCAT lists of .M3U8 retrieved 100 stations for each country and not all of them are working, but this is because I chose a free IPTV listing for each country rather than paying for my own subscription to access a private list of IPTV networks for different countries so I do keep that in mind.
I have had largely no major problems with JRiver Media Center 28 64-bit Master License for Apple macOS 12.1.0 64-bit "Monterey" yet and this includes the recently-added IPTV feature.