The following needs to be done:
@alexfoias you mentioned it takes 30min for redirection, but it's been 2h already and www.ivadomed.org gives me that:

Can you please check if everything is in order?
Sorry about that, there a problem with the configuration I tried multiple things on namecheap and readthedocs last evening without success. I'll fix it during today.
The proper way of configuring the custom domain in RTD is the following:
In namecheap, go to your domain, advance DNS and add a ALIAS record with the following info:
| Type | Host | Value | TTL |
|--------------|------|-----------------|------|
| ALIAS Record | @ | readthedocs.io. | 1min |
In readthedocs, go to your project, Admin, Domains, Add new Domain:
Domain: ivadomed.org
Canonical: [x] This Domain is the primary one where the documentation is served from
Use HTTPS: [x] Always use HTTPS for this domain
@jcohenadad We can close this issue.