Recently, YouTube changed the support for RSS/Atom feeds. Due to this change, plugins using RSS feeds generate a problem: they cannot load YouTube videos properly. In the affected plugins, a video titled "www.youtbe.com/devicesupport" is displayed with a kind (?) message: "YouTube is upgrading to a newer version, which is not supported by this device or app. To learn more and see where you can watch YouTube, visit www.youtube.com/devicesupport."
In this case, please change the path of the RSS feed to the following:
https://www.youtube.com/feeds/videos.xml?channel_id=CHANNELID'
OR
https://www.youtube.com/feeds/videos.xml?user=USERNAME