I am referring specifically to clones of Jango Fett from Attack of the Clones. Could one or more of these clones, from an original that is not Force-sensitive be Force-sensitive, without any genetic modifications (by chance)?
No, as far as I know, the clone troopers engineered from Jango Fett never became Force-sensitive. Most likely the symbiosis with Midi-chlorians could not be created in a laboratory.
In Legends, however, there were a couple of Force-sensitive clone troopers, who were created from different template, a Jedi knight. The troopers, codenamed X1 and X2 were secretly cloned from the DNA of Falon Grey, and they did possess Force powers.
The characters were created for the video game Star Wars Battlefront: Elite Squadron, in 2009.