I propose this:

sed 's;^[[:blank:]]*<.*>[[:blank:]]*\(.*\)<.*>.*;\1;' foo 

Output:

Text here that I want to keep 

This works if the tags have more than one letter, and any letter, and removing any white space at begginig and end, example:

<br> Text here that I want to keep </br> (31ca4166c37a_.76) 

I propose this:

sed 's;^[[:blank:]]*<[^>]*>[[:blank:]]*\(.*\)<.*>.*$;\1;' foo 

Output:

Text here that I want to keep 

This works if the tags have more than one letter, and any letter, and removing any white space at begginig and end, example:

<br> Text here that I want to keep </br> (31ca4166c37a_.76)