That's a task for the programmers of that Client.
We can change the channel numbers in Simple Client, because the programmer of Simple Client added this feature to Simple Client.
Please ask the Programmers of NextPVR Client, if they support custom channel numbers and if yes, what tag do they support.
If they don't support it, you can ask them if they would add that feature to the client and support the m3u tag of tvg-chno=""
We can change the channel numbers in Simple Client, because the programmer of Simple Client added this feature to Simple Client.
Please ask the Programmers of NextPVR Client, if they support custom channel numbers and if yes, what tag do they support.
If they don't support it, you can ask them if they would add that feature to the client and support the m3u tag of tvg-chno=""