I don’t have a Twitter or Instagram account, only a Youtube one and that can’t be added because Discourse within the profile preferences expects the URL to be youtube.com/c/channelname and Google disabled setting that a few days before I hit 100 subscribers.
So I don’t a channel name, I can’t set a channel name URL and at this stage it doesn’t seem I will ever be able to, as the new system is Handles, https://blog.youtube/news-and-events/introducing-handles-a-new-way-to-identify-your-youtube-channel/
Hence, unless the hard-coding of a Youtube URL in ones profile is changed to support Handles, from this point on, only people that got in early enough to actually have the old style channel URL will be able to added it to the profile and have it work.
As such, it’s not really solved, outside of I guess just adding it as a normal website URL, but then no point in having a specific Youtube or Twitter or Instagram preferences setting. May as well just remove them all and add websites as need be.