The few I checked were, but not sure if the path is defined as part of the Lemmy protocol.

Not sure if it's Boost or YouTube Revanced at fault but got the following error when I tried to open a Lemmy link to a video: https://postimg.cc/q6sW77x0

Also, the sign-up journey is a bit confused. Clicking sign up takes me to joinlemmy, which then just lands me on a home page for whichever instance I click. Might be more user friendly to prompt for a choice of instance and take them directly to that instance's sign up page. And maybe have a button for "not sure? Explore here" or something similar that would take you to joinlemmy