To run example relax_osc_st.cir, please download the device spice libs Opamps_Comparators_ST.lib
from https://www.st.com/resource/en/cad_symbol_library/opamps_comparators_st.zip

To run example Optimos_out.cir, please download the device spice libs  OptiMOS5_30V_PSpice.lib
from https://www.infineon.com/cms/en/product/promopages/power-mosfet-simulation-models/, especially
https://www.infineon.com/dgdl/Infineon-SimulationModel_OptiMOS_PowerMOSFET_PSpice_30V_N-Channel-SM-v01_00-EN.zip?fileId=5546d46256fb43b3015746ca67ac0fd3

And don't forget to add
set ngbehavior=ps
to spinit or .spiceinit to obtain PSPICE compatibility for the included (using .include) device libraries

See ngspice manual chapt. 16.13.5 for details on the PSPICE Compatibility mode.