Maybe it won't take much tweaking, but La Frite didn't like the image for sure. I'll have a look at the Balbes images as jeanrhum has suggested might be compatible when I get a chance.
The lack of a proper bootloader on the Pi4 is a bit of a disappointment, currently it'll only boot from the uSD card too (it doesn't have the USB support of the Pi3 atm) which was a bit of a backwards step. I've found uSD cards suffer from corruption on power loss far too easily. I did a project using a Pi2 and stripped back Raspian build for a touch screen kiosk and it would happen consistantly after a few power yanks. Using the uSD simply as the bootstrapper with the OS on a USB stick stopped it from occuring and made it a reliable solution -(which is the only solution that works on the Pi4 atm) .The prototype kiosk was used for over a year on site without issues.
The lack of a 64 bit OS is also hampering the Pi a bit - on paper the Pi4 should cream the La Frite, but running a simple sysbench on the two, the Frite comes out miles ahead. I understand the want to keep backward compatibility, but the option would be nice at least.