I was curious about the situation of a person who won't ever feel comfortable installing a certificate without it being easily installed through "Windows Update". Imagine that person deciding to set Secure Boot to "Off", to avoid adding a certificate. Now imagine that the time is January 2027, so the old certificates have expired, but he'll be fine because he has Secure Boot set to "Off".
Now imagine one month later, during February 2027, his BIOS battery has stopped working. He'll buy a new battery, but the default settings are active now because the depletion of the battery caused his preferred settings to be erased. The default setting of his BIOS is to set Secure Boot to "On". The certificate is expired, so he can't enter Windows 10, but could he still enter the BIOS with an expired certificate, so, with a new battery, he'll set Secure Boot to "Off" again?
I know he could pay a professional to add the certificate, but I still want to know the answer. Would the expired certificates block access to the BIOS, too?