For example, if the first use of RDA occurs as follows:
"Recommended daily allowances (RDAs) are established by nutritionists after some kind of research...."
Should the parenthetical introduction be singular or plural?
Please note whether your answer is style guide-specific.
Note: This question was already asked here: Is the acronym pluralized in the first parenthetical use?, but because the example used by the OP included a plural word (Forces) inside the initialism (RFF) the crux of this question was not answered. (I created this one because I don't have enough reputation to comment on or edit that post yet.)
Also, the above question was listed as a duplicate of this one: What is the correct way to pluralize an acronym / initialism? ; however, that topic does not answer the question I'm asking.