@73ms It's
<username>.<server_domain>.ap.brid.gy
As an example, once it goes live on production, my BlueSky account should be searchable in the Fediverse as @youronlyone.c.im.ap.brid.gy
^_^
At least based on the screenshots the Bridgy devs shared. (see: https://snarfed.org/2023-10-06_bridgy-fed-status-update-7 )