Just started experiencing this myself.
My 7yo son has a Roku TV in his bedroom and we noticed that it's rife with advertising and things that are not suitable for a child, so we made sure it was behind the Pi-hole.
The logs for the TV were eye opening - it is CONSTANTLY phoning home to log who knows what, as well is pinging a myriad of other servers seemingly unrelated to Roku.
Anyway, my son tried to use his TV yesterday and it was on the purple recovery screen and asking for network access.
I input the connection details and selected to perform the recovery, it booted into the OS and then popped up a "finalising setup" screen that sat on 0% for a while before rebooting back into the recovery screen.
Went through this cycle a couple more times until it occurred to me that maybe it was trying to phone home rather than set anything up so disabled the Pi-hole and suddenly it's able to finish setting up - remarkable!
Turned the Pi-hole back on and was able to continue using the TV.
Fast forward to this evening and once again the TV starts up in recovery mode demanding internet access...
This time we performed a factory reset and told the TV that it's not having internet access.
This behaviour is absolutely unacceptable - Roku are insisting that I permit them to spy on my 7yo child in order for him to use the features on his television.
Needless to say, we will NEVER buy another Roku product again.
I don't think you've conclusively proved that Pi-hole is responsible for the TV going into recovery mode. It may be responsible for the TV not being able to complete its setup, but there have been plenty of reports of TVs going into recovery mode from people that wouldn't have any idea what Pi-hole is. A lot of these cheap Chinese Roku TVs are just junk. I think the only way to prove that Pi-hole is responsible for it going into recovery mode is to disable it and see if it still happens.
You're right, it doesn't conclusively prove that the TV is doing it in response to being DNS blocked, but it seems highly likely and I am not prepared to allow it to spy on my kid just to verify.
If it happens while the TV has no internet access at all, I will post again.
