Hello @fpiraneo
We are aware of this issue. However, it is not completely related to us: from time to time Ubuntu key server rejects requests on obtaining the key and thus resulting in this error. Currently, it may take multiple attempts to successfully send the request and get the GPG key so it is recommended to run the installation script few times to get it working.
We are working on relocation of the keys to our repositories and updating the installation script. Due to high load of tasks it may take some time until the issue is finally resolved.
Please accept our sincere apologies for the inconvenience caused.