I followed both suggestions: I waited for the recommended time after disconnecting the battery and CMOS battery, and I also performed a full CMOS clear by pressing the open switch on the mainboard 10 times.
The reset was successful, as evidenced by the attached photo showing the BIOS settings after the clear. However, unfortunately, it didn’t resolve my Secure Boot issue. It’s still stuck on “Disabled,” even though I haven’t made any changes to enable it.