@mysterious-action-44812 - 2 issues here:
1: the ivy bootstrapper uses the ivysettings.xml when bootstrapping the full ivy classpath and this leads to class not found when the enhanced classpath itself contributes to the ivysettings.xml classpath, as it needs to in your case to provide a resolver
2: The resolver here is not ready-to-use by ivy: https://github.com/ohnosequences/ivy-s3-resolver/blob/master/src/main/java/ohnosequences/ivy/S3Resolver.java - Ivy needs a no-arg constructor / has an xml protocol for property population that is not followed here, so a shim will need to be created and published.
Both of these are pretty small fixes. It would be good to file issues if you want these to see some action.