This is due to conda-lock having some compat issues with the new mamba==2.6.0, 2.5.0 works fine, see Ben's issue on it https://github.com/conda/conda-lock/issues/906
This is due to conda-lock having some compat issues with the new mamba==2.6.0, 2.5.0 works fine, see Ben's issue on it conda/conda-lock#906