rAthena officially support only ragexeRE clients, but ragexeRE from version 2018-07-04 and newer not supported by rAthena.
If you need new clients, you can try ragexe, but it may not works, because version checks in server code based only on ragexeRE versions.
If you have issues with nemo, probably you using outdated version? Try from here https://gitlab.com/4144/Nemo