Wasn’t there just recently a discussion about replacing curl through wget because of reasons (snap curl has no write access to most directories, is not allways available) in the actual installer? Can it be that the very same reasons make the installation attempt for the installer script go poof? Does the installation document need an actualization? I think it doesn’t make sense to replace curl, which may not even be available on all installations, through wget in the actuall installer and then leave curl in the install document.
As a test:
wget -O roonserver-installer-linuxx64.sh https://download.roonlabs.net/builds/roonserver-installer-linuxx64.sh
Does this command to download the installer work (or show a reason why it fails)?