Ask HN: Should authors disclose if they are paid to write a blog post?
Youtubers do this all the time.
Computer magazines in the day used to (probably still do) evaluate competing equipment. The equipment was provided by the producer. The Producer would cherry pick the best.
This is why organizations like consumers reports are respected, they BUY everything they test, so you know it was not a custom build.
I believe YouTube requires the disclosure.