Hi there, @Erss.
QuickBooks Desktop 2019 uses Internet Explorer rendering engine to load certain web-based modules, such as payments, payroll, and bank feeds. So it will only prevent those internet-dependent forms and UIs from loading properly.
Since QBDT 2019 is already discontinued, you can only use it in offline mode. Therefore, the script error you're seeing only affects online features that are already unsupported. Rest assured, it's safe to ignore these script errors, as they won't affect your daily workflow with QBDT.
Older versions of QBDT are still using Internet Explorer 11, but they're not compatible with newer versions of Windows that have ended their Internet Explorer browser, due to the birth of Microsoft Edge. Learn more from this article: Use our built-in browser in QuickBooks Desktop.
The best option is to purchase the latest QuickBooks Desktop version. You'll be able to use online features without any problem.
Feel free to leave a reply if you have additional concerns with QBDT. We're always ready to help.