I would trust a Matrix client like Element / Schildichat over Signal and Telegram. But if we are only considering the latter, I would pick signal (like many other comments have mentioned).

Trust doesn’t matter if no one uses these platforms to message you.

I persuaded my friends into trying other messaging platforms but they ended up flocking back to Whatsapp because their contacts are not on Signal and definitely not on Matrix. Also normies may find Element/Matrix difficult to use. Almost all of them have Telegram accounts and believes it’s more private than Whatsapp, also apparently they use it as a content downloading app than a messaging app.

On android there’s libretube. I think it has some recommendation/related content suggestion functionality in the app.

On the web version of piped, i do not know of any recommendation feature.