If you run
you'll see there are [System data] config directory and [User data] config directory
Config directory: /etc/mc/
Config directory: /home/<username>/.config/mc/
First is system-wide, the second is User specific.
The second one seems to be dependent on user's home location;
in other words, it is bound to it. That means if you want to (temporarily) start mc with an alternate config as the same user you cannot do it w/o changing (and
exporting) the HOME variable prior to it.
This 'Changing-HOME-prior-to start' workaround, though does the trick,
is hardly acceptable, as it well... does modify the user HOME.
Do you think there is a way to either
Change the user config dir dynamically before the mc starts (command line option would be the most appropriate thing, but it does not seem to be there)
Restore 'natural' HOME for user just after mc started, if changing HOME before is the only way to change user dir location
mc instances configured differently must not interfere each other if running simultaneously.