Checked NowTV on the previous NowTV release on my 2016 iPad Pro on iPadOS 13.6 - running fine. Updated to 10.14.0; still running OK, though I only tried it for five minutes or so.
So not a universal problem....
Try uninstalling the app, powering down the iPad, waiting two minutes, powering up again, and reinstalling the app. What you did before, but maybe you didn’t include the power down? That might help.
Thanks for your suggestion. Unfortunately, I tried that and didn’t work. It might not be universal, but it could affect the non-Pro iPads. If someone with the same device doesn't experience the same issue (almost instant crash), then I’d try restoring the device.
My iPad has just offered me 13.6.1, the seemingly inevitable codicil to every Apple point release.
It might be worth downloading that and trying it, before going much further.