profile location on linux

On linux, in the past, firefox kept all its data in home/{user}/.mozilla. This was changed at some pont to spread the data out into /home/{user}/.config, /home/{user}/.cache and maybe another place but when the change was made existing data was not moved and remained in /home/{user}/.mozilla. For my purposes I prefer to see the data in the old location. I make heave use of profiles and I store them on an encrypted partition and I have firejail setup to give access to the old location. Whart does Firefox look at to determine whether to look in the new locations or the old location? What is the new location of profile.ini?