Can the EPC2204A be used with the LT8391?
this controller should work with GaN. We recommend the following:
By the way there is also a “A” faster version of this controller that can go up to 2MHz: LT8391A (Rev. A) (analog.com)
At those frequencies maybe a smaller device than EPC2204A might work better like the EPC2252: Automotive Qualified 80 V, 75 A GaN FET (epc-co.com)
In any case I would recommend to use our selector tool here to get a recommendation for your specific conditions:
GaN FET Selection Tool for Buck Converters (epc-co.com)