I recently faced this error when trying to build an Elixir project.
== Compilation error in file lib/swoosh/adapters/xml/helpers.ex == ** (ArgumentError) lib file xmerl/include/xmerl.hrl could not be found (elixir 1.13.4) lib/record/extractor.ex:41: Record.Extractor.from_lib_file/1 (elixir 1.13.4) lib/record/extractor.ex:18: Record.Extractor.from_or_from_lib_file/1 (elixir 1.13.4) lib/record/extractor.ex:5: Record.Extractor.extract/2 lib/swoosh/adapters/xml/helpers.ex:5: (module) (elixir 1.13.4) lib/kernel/parallel_compiler.ex:346: anonymous fn/5 in Kernel.ParallelCompiler.spawn_workers/7 could not compile dependency :swoosh, "mix compile" failed. Errors may have been logged above. You can recompile this dependency with "mix deps.compile swoosh", update it with "mix deps.update swoosh" or clean it with "mix deps.clean swoosh"
If you can the error above on Fedora, you probably need to install the erlang-xmerl package.
By default, the firewall will prevent connection to your 0ad server. To adjust that, you need to open up the port 20595 (UDP). This three lines create a Firewalld service called 0ad, attach it to the default zone and reload the firewall:
$ sudo firewall-cmd --permanent --new-service=0ad --set-description="0ad, A free, open-source game of ancient warfare" --add-port=20595/udp
$ sudo firewall-cmd --zone=FedoraWorkstation --add-service=0ad --permanent
$ sudo firewall-cmd --reload