Just to close the loop, these changes have now been implemented in master and will be included in ParaView 5.9. Below is the output generated using --help by pvserver executable from the nightly binaries. The launcher options are list first, followed by the standard executable options (in this case, pvserver options).
> ./bin/pvserver --help
Launcher options:
--print Print modified environment.
--system-mpi Use MPI implementation available on the system.
--mesa Use Mesa GL for rendering.
--backend <backend> Specify mesa backend.
Available backends:
llvmpipe
swr
pvserver options:
--client-host=opt
-ch=opt Tell the data|render server the host name of the client, use with -rc.
--connect-id=opt Set the ID of the server and client to make sure they match. 0 is reserved to imply none specified.
...
You should be able to test these out using the latest nightly binaries for Linux.