Tested to work on: Firefox.
Accountless youtube allows you to subscribe to channels without a google account, the subscription list is saved locally in extension storage, the feed will show up in the subscriptions tab in chronological order, and the subscribed channels will show up on the side bar/pad/guide on the left. The subscribe button is automatically replaced so you can just click Subscribe like you normally would to add a channel. The extension scrapes the video data from youtube, it will not take into consideration older videos due to youtube's annoying api, however that is usually not necessary anyways. The extension replaces the usual feed, side bar, and button with, its own versions that are easier to work with, however the replacements are not perfect so this is why you might notice a slightly different font/behaviour.