Likewise, there's not a chance in hell I can pull off "hey y'all", well maybe if I was wearing a cowboy hat... :)

In any case, I use "Hey peeps..." (peeps -> people), which doesn't offend people (afaik).

The idea that it's sexist or problematic to address a mixed group as "guys" doesn't quite seem to have crossed the Atlantic yet, but I'm sure it's coming. The U.K. is never too far behind American cultural trends, especially the insane ones.

Probably, I've been in the US for ~20 years.

Someone can also choose to be offended or not. Apparently this has been forgotten in modern times.

I thought of the same thing, but there are these: https://en.wikipedia.org/wiki/Peeps

You can try to homogenize language and culture to suit your own sensibilities. Since I view "guy" as a gendered term, then that's clearly the only acceptable definition and interpretation of the term. Other people's usage is obviously problematic and I want to compel them to change their language to meet my requirements and sense of acceptable terminology.

Alternatively you can embrace the fact that people's language is their own and acknowledge that the person's intent here does indeed matter. You don't need to adapt the same language that they use, but you could be mindful that people speak differently than you and that your discomfort with terminology is sometimes maligned.