Selfhosted

I found out how to get the list of users registered on my instance. Assuming docker-compose based installation, to access the database via CLI:

cd LEMMY_FOLDER
docker-compose exec postgres bash
psql -d lemmy -U lemmy
select name from person where local=true;

The db also contains all users known from federated instances; you can look for one e.g. via

select name,actor_id,instance_id from person where actor_id='https://social.cyb3r.dog/u/senicar';
  name   |              actor_id              | instance_id 
---------+------------------------------------+-------------
 senicar | https://social.cyb3r.dog/u/senicar |         398
(1 row)

and look for other users on that same instance:

select name,actor_id,instance_id from person where instance_id=398;

There are plenty of other queries you can do on the db, e.g. to figure out which instances have most banned users, which instances are presumably private (have less than 5 users known to you), max instance_id to see to how many instances you are connected, etc.