Last time I tried to build 202311 on illumos it failed due to a number of conflicting type definitions. I haven't had the time to get back to it and see what is going on there.
If you want to try building it yourself then you should be able to just take the upstream tianocore 202311 tag and cherry pick the last three commits from the il-edk2-stable202308, resolving any conflicts, then start from there.
Otherwise I can take a look at the weekend. In the past I've updated this in OmniOS first then pushed the branch to illumos after some period of soak testing.
Andy