Docker installed on localhost, iframe api, which domain should I use?

I followed this guide to install jitsi in my development environment on localhost (Windows 10):

I only modified the following entries in .env file, to test jwt with iFrame API:

# Enable authentication
# Enable guest access
# Select authentication type: internal, jwt, ldap or matrix
# JWT authentication
# Application identifier
# Application secret known only to your token generator

Now I would like to use iFrame API with the local installation, but I do not know which domain I should use:

          window.onload = () => {
		  const domain = '';
            const api = new JitsiMeetExternalAPI(domain , {
              roomName: "my_jitsi_app_id/sampleroom",
              parentNode: document.querySelector('#jaas-container'),
							jwt: "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJjb250ZXh0Ijp7InVzZXIiOnsiYXZhdGFyIjoiaHR0cHM6Ly9yb2JvaGFzaC5vcmcvam9obi1kb2UiLCJuYW1lIjoiSm9obiBEb2UiLCJlbWFpbCI6Impkb2VAZXhhbXBsZS5jb20ifX0sImF1ZCI6ImxvY2FsaG9zdCIsImlzcyI6Im15X2ppdHNpX2FwcF9pZCIsInN1YiI6ImxvY2FsaG9zdCIsInJvb20iOiIqIiwiaWF0IjoxNjg0MjQ2MzU5LCJleHAiOjE2ODQyNTM1NTksIm5iZiI6MTY4NDI0NjM1NH0.NaeOf_wRChGpsHNnjuTvn3E12nrgDltK9rFUGQOegp4"

I get the error “Sorry, you are not allowed to join this call” , but I guess this happens because I am not connecting to my localhost docker installation. What should I use as domain?

The value you put in PUBLIC_URL without the https://.

I would like to test it on localhost, is it possible?

try localhost then … if you are running it on https://localhost

with domain = localhost I get this error (from the browser console):

GET https://localhost:8443/external_api.js net::ERR_CERT_AUTHORITY_INVALID

You need a valid certificate there.
Then do it with the domain from PUBLIC_URL and put it in /etc/hosts to point to localhost, if you have a valid certificates there.