Main firmware version 90.06 for Axpert Max 8 kW or 5 kW (NOT 7.2 kW). Because this is a 90.xx version number, it may be experimental or designed to fix one particular bug.
For models with removable display, not the newer "round display" models.
Note that this is more recent than firmware versions 90.07 or 90.10.
dsp.hex dated 2022-02-11. Use at your own risk.