In post-Roman Western Europe, what is the earliest evidence we have of anyone realizing their language(s) were evolving from Latin and/or diverging from each other?

Not to discourage discussion, but a similar question has been posted here with answers from myself and u/LosDosTacosLocos:

A few important notes:

Romance languages did not evolve from Latin, but from the Vulgates, non-written non-standard Latin that had great regional variation already and formed a continuum with other Italic languages of the time.
The few people who were literate used standard written Latin in writing. This doesn't mean they were speaking this form of Latin at home, too. Diglossia was typical of Roman writers - where written and spoken language are distinct forms. So even classical Romans would be aware of a distinction here, though they wouldn't be speaking the regionally-affected Romance languages I think you're asking about.
During the early middle ages texts are in Latin, with the earliest Romance attestations in writing coming in the 9th to 12th centuries. This doesn't mean they didn't exist prior to this - just that there was only one written standard at this time among the few people actually doing writing. Language is constantly changing.