I've got a solution, I'm in dark mode as I type this:

If you're not using chrome, download & install it.

In the browser web address bar (where you enter website addresses) type or copy in the following exactly: chrome://flags

Press enter

After the chrome://flags address opens, you should see a search bar at the top of the page

Search for 'dark'

You should see an option to force all websites to be in dark mode (even if they don't offer dark mode)

Make sure that option is enabled, it's called Auto Dark Mode for Web Contents

You should see a button after making this change, the button wants you to relaunch Chrome, if you don't see the button just close chrome and relaunch it manually.

After re-opening Chrome, QBO should be forced into Dark Mode, even though it's not offered directly via QBO.

I actually really like QBO, but the support is lacking (no offense), please reach out if anyone needs further assistance, bookkeeping support, or anything else: [email address removed]

Thank You!