Filter nodes by today's date
Figured this out.  Have to add the following 2 filters:

operator is "Is greater than or equal to" value is today

AND 

operator is "Is less than" value is today +24 hours

Notes: 

Must use "Is greater than or equal to" to include today at midnight and must use "Is less than" to filter out tomorrow at midnight.

It does not matter what value type you select, machine readable or offset.

The value "today" literally returns the time of midnight on today's date.  This means setting operator Is equal to "today" only returns results dated on exactly midnight of today, hence why zero results were returned.

SQL for "today" taken from Views query:

DATE_FORMAT(('2020-03-29T07:00:00' + INTERVAL -25200 SECOND), '%Y-%m-%d\T%H:%i:%s'))

"+ INTERVAL -25200 SECOND" is -7 hours correction for my time zone so time is T00:00:00 or midnight.