Just like the solution for The Sentinel, the easiest way to achieve this is to locate an extreme planet, find a safe place and buckle down, unless you want to attempt the harsh conditions. As of right now, this can be accomplished by staying in the safe space and simply waiting for the days to go by. Robust status is achieved after 20 days (sols) have gone by, which is the 7th milestone for Extreme Survival. The duration of one day will vary based on the planet. When I did this, one sol lasted between 11-12 minutes. Time will not pass if you are in the menus looking at discoveries, milestones, log, etc. Time WILL pass when looking in inventories if need be.