That might be an issue with clearml itself that fails to send proper resources if you change the path, that kind of path modification can be a hussle, if you have a domain name available I would suggest making a subdomain of it point to the ip of your clearml machine and just add site-enabled on nginx to point on it rather than doing a proxy pass

I tried via nginx but it doesn't work. This is the location configuration:
location /clearml/ {
proxy_pass None ;
}
in this way via the web the portal seems to load but then nothing is displayed.
If instead I change the location to just "/", then it works. Am I doing something wrong?

I will try as you indicated. Thank you

You need to set a specific port for your clearml server and then just set a rule in your reverse proxy (eg. nginx) to make point the specific route you want toward that port