I'm on Windows 10, desktop app, not the store app.
Windows 20H2, OS Build 19042.870
I have the exact same issue. I copy clean text with no nbsp characters from Notepad+ into a code block in Evernote and it creates those nbsp's. Example below.
Before in code block:
<a href="" title="">
After Paste in code block:
<a href="
/service-specials-coupons
" title="">