It goes to the person who wrote the code.
Something is broken
Include your channel handle and roughly when it happened. If an upload failed, the exact message matters more than a description of it.
A comparison page is wrong
These are compiled from public documentation and go stale. Point at the line and it gets corrected, including when the correction favours the other product.
A methodology threshold looks wrong
This is the most useful email I can get. The thresholds are published so they can be argued with.
You want your data out
Ask and you get an export. You do not need a reason and there is no retention flow to sit through.
You want an account deleted
Ask from the address on the account. Deletion removes the account, the channel connection and the stored tokens.
Security
If you have found something that exposes another creator’s data or their YouTube access, mail the same address with SECURITY in the subject and it goes to the top of the pile. Please do not post it publicly first.