Yes, it is best if you use the "unique ID", available in the source HTM in case the URL contains a "human readable" version.
"/user/"
"/channel/"
"/playlist?list="
I think the newer slug format for channels is "/c/" in which case I think you do have to extract it from the HTML source, but they now include the feed URL anyway.
<link rel="alternate" type="application/rss+xml" title="RSS" href="FEED_URL">