renewables will probably be enough to supply all our needs and more by the 2030

This seems extremely optimistic! Electricity production from coal has been rising steadily for decades :( https://www.statista.com/statistics/1082201/coal-fired-electricity-generation-globally/

What mergefs options did you pass in fstab? Check the mount options on GitHub. It took me way too long to discover ignorepponrename=true. In your case moveonenospc could be relevant.