@north,
In his celebrated work "Philosophy and the Mirror of Nature", Richard Rorty gives a lengthy and thorough exposition of the failure of philosophers to find any agreed "fundamental substrate" on which to based epistemology. Irrespective of this failure by philosophy,
just over the last century or so, physicists have agreed on a
pragmatic listing of what they utilize as "fundamental particles", but we should note that their theoretical "status" is forever subject to revision.
So the question boils down to whether the term "fundamental reality" has
any value at all, since it is undefineable either philosophically or scientifically. IMO such a term is merely a marker for a hypothetical metaphysical position...a "God's eye view"... which endeavors to
ultimately transcend observer and observed. As such it carries all the religious baggage of "absolutism" without actually evoking a deity. The alternative term "relative reality" is the pragmatic and possibly the
only viable alternative.