I'm not familiar with that box, but I'm guessing you won't be able to change it if it's built into the UI of the box.
You can however, install other apps as I'm sure you're aware. You just won't be able to change the functionality of the OS most likely.
But without an accurate description of what this button is you speak of we won't know for sure.
Can't you just add an app to the shortcut of your launcher? Most boxes allow that.
Consider using a different launcher.
You should have access to the Google play store to download whatever iptv app you want. You probably just can't replace the IPTV app cooked into the home screen, but you don't have to use it. At worst if there's no Google play you can download the apk file off the internet and install it on your box with a thumb drive
If there is an app store option on your box you can go to it and see whats under category IPTV and download whatever client there is and use it
Look in the settings menu, it might have an item that specifies which app auto launches.
Did that when I got tired of chasing nonexistent "problems" related to elderly parent and IPTV, switched the default app to Sling TV and haven't gotten a phone call about the damn thing since.
As the title says, does someone know how I can change the IPTV app that opens when I click on the 'IPTV' button?
Model: Smart Box 4K Slim
Android version: 7.1.2