Thank you for your question.
In the example you describe, I would break before the baseline symbol of comparison and also before the fraction line.
Your desire to keep the fraction unbroken is considerate, and I understand why you would want to do that. One of the reasons we follow a hierarchy for dividing a long mathematical expression is to keep logical units of the expression together/unbroken for ease of reading.
HOWEVER, another of the reasons we follow a hierarchy for dividing a long mathematical expression is to make revisiting the expression intuitive, and we do that by always dividing at the highest priority/hierarchy level first (i.e., a baseline symbol of comparison). That way, wherever possible, an expression that spans multiple braille lines will have at least one line that begins with a baseline symbol of comparison.
Please let me know if that helps or not.
P.S. For what it is worth, I understand the statement that "Usually the best place to break is before a comparison sign" to mean that a comparison sign is not a good place to break when it is part of something other than the baseline/main expression (e.g., an equals sign in Sigma notation, like that shown in GTM §7.9).