I would like to know this too. I am unable to set up the Ambiclimate integration despite following the instructions.
I first created an app here (https://api.ambiclimate.com/clients), where the callback url is the remote Nabu Casa link that looks like https://<unique_nabu_casa_link>.ui.nabu.casa/api/ambiclimate
Then I added these lines into the configuration.yaml, saved it, and restarted:
# Ambiclimate
ambiclimate:
client_id: xxx
client_secret: xxx
After that, I went to Configuration > Integration > Add Integration > Ambiclimate:

Somehow, the Callback URL that shows up is the local link, instead of the external Nabu Casa link I used to create the app in Ambiclimate. Following the link just shows me a JSON 404 error:
{
"description": "not found",
"error": 404
}
Appreciate any help I can get to setup the Ambiclimate integration!