I can’t use my custom URL that YouTube provided to link my channel on my profile’s social links. This has been mentioned before here, but it probably fits better into the bugs category because it is likely unintentional, and the post was three years ago.
Roblox only allows the word “user” while many other channels use “channel” or “c” instead. Due to this, any channel with a different extension wouldn’t be able to be linked. Sometimes, the old links still work if you still have it, but most people will forget the random code at the end.