I've used python, pywebview and html/css on a (super) simple application recently. pywebview will use system installed web browser, rather than ship entire chromium. So maybe check that out.
System installed web browser sounds like a common mistake. Easy to deploy and develop for it, hard to maintain. In the end you'll end-up with frustrated customers when it comes to security nightmare. Better ship that Chromium, it will save you a lot of negative karma.