Why did backspace stop working in chrome and ff on ubuntu?

Question

Google Chrome

At some point, backspace stopped working to return to the previous page in browsers (chrome, firefox) on ubuntu on both laptops (not simultaneously, with an interval of 3 weeks). When you click on backspace, a message is shown:

to go back press alt + →

Any ideas what it is and how to get it back?

Answer 1

What caused the back button change in browsers?