I still have the old Q5, which I've been using as an occasional backup media player; it's been often used for accessing Youtube. Recently, its Youtube application apparently stopped being supported by Google; any attempt to run it generates only a "This action isn't allowed" error. I do know that a workaround on some players has been to download an old version of a Youtube TV player APK from APKmirror, and installing it as a second Youtube app. I've browsed various older Youtube APKs on apkmirror.com - https://www.apkmirror.com/uploads/?q=youtube-for-android-tv-android-tv - tried installing several versions, but the Q5 won't accept any of them. Would anyone happen to know what, if any, Youtubes may work with the Q5?
(There is the unofficial "Smart Youtube" application as well, but I'm hesitant about third party apps that require account info...)