I can’t backup my iphone 8. I’ve exhausted ALL OPTIONS!

If you have tried all of the options listed in How to back up your iPhone, iPad, and iPod touch - Apple Support without success, be sure to use the Contact Apple Support link at the end of that Support Article.

What's the issue? As I understand you can't use both local and iCloud backup? So... Error message/OS/iTunes version if Win/etc.?

You are welcome.