I have a boot.img file that Magisk says "unknown/unsupported image format" trying to patch. It's a valid working boot image and can be flashed and booted. It's also the latest android 13 boot image for my device.
I have also tried with the full zip file. No change.
Device: Pixel 6a Android version: bluejay-t1b1.220819.007 Magisk version name: 25.2 (25200) 33
The developer seems to want all reported issues to be with a build compiled from source, which is beyond my capabilities.