At RSS Reader section https://support.google.com/youtube/answer/6098135?hl=en there is an option to export to an OPML file your subscriptions. Then, looking at the contents of the OPML you can extract the feeds, and the structure of each feed is:
https://www.youtube.com/feeds/videos.xml?channel_id=XXXX
So you could generate new feeds from this structure if you know the channel id. This kind of feeds are not getting the “https://youtube.com/devicesupport” error, so I expect they are going to keep working.