Set up your Free Select Tool then go to Edit ➤ Preferences a new window opens, at Tool Options click on Save Tools Now, then OK at the bottom of that window.
This should keep your tools options (re-start GIMP to see if it works, it should keep your free select with the new setting).
(red arrow = to do first)
This should keep your tools options (re-start GIMP to see if it works, it should keep your free select with the new setting).
(red arrow = to do first)