Must have Rangers TV and Celtic TV, and preferably allow multiple simultaneous connections (even if there's an extra charge, that's ok)
I used Flawless, which meets all my criteria, but every single channel buffers every 10 seconds, even when my internet is working perfectly elsewhere.
EclipseIPTV, 2 connections , vpn allowed.
What device are you using ? I actually never have any issues with channels buffering but I use stbemu or the app.
Try vpn also. ISP could be throttling you.
SmoothStreams has all NBA and NHL games (is that Celtics and Rangers?). They allow 3 IPs. 720p60fps.
Turn off your ISP blocker/shield/family filter.
That's your problem with flawless unless you are in aus or nz