Secure Boot configuration is usually stored in flash, not battery-backed CMOS, so on most boards won't be wiped if you simply remove the battery. But if you do

Secure Boot configuration is usually stored in flash, not battery-backed CMOS, so on most boards won't be wiped if you simply remove the battery. But if you do have physical access you can simply rewrite that variable in flash to disable it - doing so will change the TPM measurements and so Bitlocker (or whatever) will complain, so it's not silent.