@nebulon, @BrutalBirdie
Thx to both of you, the call is now working.
curl -kX POST -H "Content-Type: application/json" https://my.smthg.com/api/v1/apps/install?access_token=857f7d7eb583cfb951e5a50c75a762b94304d4ba50d4a0c94950643eaab7959a -d '{"appStoreId": "io.n8n.cloudronapp@2.37.0","subdomain": "workflow","domain": "somethg.com","accessRestriction": {"users":[],"groups":[]}}'
{
"id": "c6c79d78-7c7c-414b-acf7-8b5cc39370ed",
"taskId": "269"
}
It needed obviously the header, but also I thought reading the API specs that accessRestriction could be null. It is not the case, so I used @BrutalBirdie assignment (empty users and groups) and the call succeeded.
Once again thank you very much.