Frozen atoms in NPT ensemble

GROMACS version: 2019.1
GROMACS modification: No

Dear all,
I want to run MD simulation for a protein in membrane, with a single residue frozen completely. For membrane simulations, I have to use semiisotropic NPT ensemble. However, NPT does not work with frozen groups. I have found that previously energy group exclusions could be applied, which are now not supported. How can this issue be solved?

Thank you in advance,

You will need to use a version that supports the group scheme (which I thought 2019 did, but if not, roll back to 2018) or otherwise simply use very strong position restraints. Freezing is entirely unphysical, anyway.