Acutally, If I decrypt wil6210-lhg-span2.8.brd and put it under /lib/firmware/ with the seed 0x967e9839, it fails with:
Fri Dec 20 15:39:08 2019 kern.err kernel: [ 928.103612] wil6210 0000:01:00.0 wlan0: wil_fw_verify: ERR[ FW ]checksum mismatch: calculated for 3588 bytes 0x6b37878a != 0xd414aa93
Can't I replace the boardfile like that?
Edit: Oh, you had the same problem. ^^