Today I write from the day job, where I am researching the question of
how can I go about producing random UUIDs, in dozens or hundreds, inside
an XSLT pipeline, without extension functions in Saxon. The Java
randomUUID() function works nicely when its available, but I need to
distribute the capability for SaxonHE and eventually SaxonJS.

We do not have an available implementation of RFC 4122 v4 random UUID
in pure XSLT do we, free to use (and study)? I know the functional
nature of the language makes randomness, um, problematic (when isnt
it?),

HE 10 with higher-order function support (which is not available in HE
9.8 and 9.9) has at least support for fn:random-number-generator, Saxon
JS 2 also supports that function. I have no idea whether that helps with
generating random UUIDs.