The ability to unlock the bootloader is actually irrelevant in this case. I want the source code because it is my right. I might find away to boot custom code or I may not.
And what will you do with it exactly? Without unlocking the bootloader, it’s basically useless. You should concentrate your efforts on seeing if you can unlock the bootloader first.
Either way I still want the sources to study at least.
There wouldn’t be anything interesting about those sources, except the binary blobs/DTB. Unless you’re expecting to find some malware or something. If you’re really interested in studying the kernel/Android sources, you can always head to source.android.com or kernel.org. There are also more interesting sources over at LineageOS and GrapheneOS.
As for streaming services I use Jellyfin so its not a big deal.
Then why did you even bother buying this box? You’d have been better off using a Raspberry Pi or some HTPC, where you could load any opensource distro or even easily compile your own, and have a far greater deal of flexibility and freedom.