OK so I nuked cs on a machine with ubuntu 22.04 where I got the new scala runner to work and then just reinstalled and it stopped working 
Scroll further down to see the resurrection of the failure…
$ scala
Welcome to Scala 3.5.0 (21.0.4, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
scala>
$ cs version
2.1.10
$ cs uninstall --all
Uninstalled amm
Uninstalled coursier
Uninstalled cs
Uninstalled sbt
Uninstalled sbtn
Uninstalled scala
Uninstalled scala-cli
Uninstalled scalac
Uninstalled scalafmt
$ curl -fL https://github.com/coursier/coursier/releases/latest/download/cs-x86_64-pc-linux.gz | gzip -d > cs && chmod +x cs && ./cs setup
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0
100 19.9M 100 19.9M 0 0 4362k 0 0:00:04 0:00:04 --:--:-- 5763k
Checking if a JVM is installed
Found a JVM installed under /usr/lib/jvm/java-21-openjdk-amd64.
Checking if ~/.local/share/coursier/bin is in PATH
Checking if the standard Scala applications are installed
Installed ammonite
Installed cs
Installed coursier
Installed scala
Installed scalac
Installed scala-cli
Installed sbt
Installed sbtn
Installed scalafmt
$ scala
[warning] MainGenericRunner class is deprecated since Scala 3.5.0, and Scala CLI features will not work.
[warning] Please be sure to update to the Scala CLI launcher to use the new features.
[warning] It appears that your Coursier-based Scala installation is misconfigured.
[warning] To update to the new Scala CLI runner, please update (coursier, cs) commands first before re-installing scala.
[warning] Check the Scala 3.5.0 release notes to troubleshoot your installation.
Welcome to Scala 3.5.0 (21.0.4, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
scala>
$ cs version
2.1.10