Disclosure: I am the author of FlashDim
You can check out FlashDim:
If you really want go down the rabbit hole, a professional proxy service with deep packet inspection is inevitable.
If it's more like for parental control for a younger kid, Pihole is your friend. You ...
You can run ffmpeg also on Android by utilizing environment like Termux. Install it with a command like:
pkg install -y ffmpeg
and grant it access to files.
Rooting may or not be required depending ...