One of the problems is the following issue in jetty: jetty/jetty.project#12913.
Because of that, the resources from a webjar are treated as an alias and 404 is returned instead of the resource

Hello @OptimumCode , I would like to ask about the status. Is there something on your list of things left to do (except form the obvious failing checks)? I am thinking to maybe contribute a bit if I could in a way

Hi, @olindenaus, the help would be very welcome) I haven't had much free time recently to continue looking into the PR, unfortunately...

First of all, the new Jetty version was released, and it contains a fix for jetty/jetty.project#12913. We should see fewer failing tests. The rest of the problematic places can be found in the PR description (unfortunately, I have not had time to look closely at all of them). I think the one that causes the most test cases to fail is the cookies problem - the old approach to remove them does not work anymore. The test client (which is reused between tests) keeps cookies from previous tests, and it causes failures.
The second thing is to make compression work with resources. The compression is implemented on the servlet output stream level, but resources are handled by a Jetty-specific handler (which expects different objects as input). I have tried to create a wrapper around the output stream, but it did not work (CompressingResponseWrapper in JettyResourceHandler.kt).

Hello @OptimumCode, thanks for your reply, I will try to contribute when I find some free time during these days.