/etc/ is in primer3 2.4.0-1ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/etc/primer3_config/
/etc/primer3_config/dangle.dh
/etc/primer3_config/dangle.ds
/etc/primer3_config/interpretations/
/etc/primer3_config/interpretations/dangle_i.dh
/etc/primer3_config/interpretations/dangle_i.ds
/etc/primer3_config/interpretations/loops_i.dh
/etc/primer3_config/interpretations/loops_i.ds
/etc/primer3_config/interpretations/stack_i.dh
/etc/primer3_config/interpretations/stack_i.ds
/etc/primer3_config/interpretations/stackmm_i_mm.dh
/etc/primer3_config/interpretations/stackmm_i_mm.ds
/etc/primer3_config/interpretations/tetraloop_i.dh
/etc/primer3_config/interpretations/tetraloop_i.ds
/etc/primer3_config/interpretations/triloop_i.dh
/etc/primer3_config/interpretations/triloop_i.ds
/etc/primer3_config/interpretations/tstack2_i.dh
/etc/primer3_config/interpretations/tstack2_i.ds
/etc/primer3_config/interpretations/tstack_i.dh
/etc/primer3_config/interpretations/tstack_i.ds
/etc/primer3_config/interpretations/tstack_tm_inf_i.dh
/etc/primer3_config/interpretations/tstack_tm_inf_i.ds
/etc/primer3_config/loops.dh
/etc/primer3_config/loops.ds
/etc/primer3_config/stack.dh
/etc/primer3_config/stack.ds
/etc/primer3_config/stackmm.dh
/etc/primer3_config/stackmm.ds
/etc/primer3_config/tetraloop.dh
/etc/primer3_config/tetraloop.ds
/etc/primer3_config/triloop.dh
/etc/primer3_config/triloop.ds
/etc/primer3_config/tstack.dh
/etc/primer3_config/tstack2.dh
/etc/primer3_config/tstack2.ds
/etc/primer3_config/tstack_tm_inf.ds