If you're down to use Piped as a YT front-end, there's an RSS icon on every channel page in the top right corner.
If you want to use YouTube directly, use the following link and append the channel ID of whatever channel you want to follow: https://www.youtube.com/feeds/videos.xml?channel_id=
Another alternative would be using something like FreeTube, which can use RSS to fetch subscriptions (but doesn't by default unless you're subbed to a high number of channels).