When I signed up on this site, the first thing that happened was it popped up a message giving me a login key and asking me to save it. The problem is the key was shown in an alert dialog (or something similar) which didn't allow me to copy and paste the key. I'm using Chromium 79.
Please display this information on a regular web page, and consider expanding the explanation, e.g. mentioning the fact that the key can also be retrieved from the user profile at a later time.
Or perhaps it could go straight to the profile page (so the user can edit other details), with a one-time introduction message or something like that.
update May 2020: we have removed the popup altogether which side-steps the issue. You can copy the login key from your profile, and a system notification prompts you to do so.
Very sensible suggestions, thank you.
I'll update this post when we release a fix.