With your HFSS 2022R2 installation you can find a file called "What's new in Ansys Electronics Desktop 2022 R2" in the documentation folder. Under known issues you can find this section:
"611491 – Potential MPI failure on Linux (most commonly seen on Ubuntu) for distributed
simulations. Users can bypass the issue by setting the following environment variable
prior to opening Electronics Desktop and launching the simulation: I_MPI_SHM_LMT =
shm"
This environment variable solved the error code 149 issue while starting the MPI distributed solver on ubuntu machines for us. Therefore, the frequency sweep simulation can run on multiple cores, not just one.