youtube-dl is "a command-line program to download videos from YouTube.com and a few more sites."
AllTube is a GUI for youtube-dl
Note: As of 2020-10-31, it's no longer possible to export subscriptions through the above link. Google Takeout does allow a list of YouTube subscriptions to be exported. Unfortunately, this list is in a format (JSON) unsupported by feed readers or either alternative below.
To manage all videos in a YouTube playlist (i.e., the classic YouTube interface), add
&disable_polymer=1 to the end of its URL.
FreeTube is "a YouTube client for Windows, Mac, and Linux built around using YouTube more privately." Because subscriptions and watch history are stored locally, no account is required.