Every once in a while I check the motherboard manufacturer's website for bios updates. Usually the BIOS version is listed in one of the first boot screens. There are two problems with this:

First I have to reboot the machine to do this. This is not always a convenient thing to do.

Second I have to be in front of the machine. I maintain a number of servers and workstations that are spread apart geographically.

Fortunately there is a solution if the computer happens to be running Linux. From the command line I type:

sudo dmidecode -s bios-version

Here are some examples from the machines I own/maintain:
ASUS M2A-VM HDMI ACPI BIOS Revision 2101
A11