Took me a while, because I couldn’t remember how I’d imported the LastPass data. I recreated it by following their promps, and I suspect that what I did was directly replace the information in Bitwarden (I’m not sure, but I’d expected a prompt to save or download a file, and didn’t get one). So I went back to LastPass and followed the directions for exporting to a csv file; what I was a display of a file on hte lastpass site – export.php, whose first is this:
url,username,password,totp,extra,name,grouping,fav
But I also got as a download a file that looks incomplete, named lastpass_vault_export.csv, which has only 13 lines in it. The first line same headers, and in the url column are full urls, e.g. http://frederictonartsalliance.ca/
I hope this tells you something helpful . . . and I hope I haven’t reverted my bitwarden vault back to the current state of the LastPass one.