Affected versions

• 88.0a1(2021-03-28), 88.0b8, 87.0;

Affected platforms

• Win10, Ubuntu 20;

Steps to reproduce

1. Launch Firefox, access about:preferences#general
2. Scroll down to the Applications section;
3. Click inside the Search File types or applications field;
4. Press the TAB key a few times;

Expected result

• keyboard navigates through the table bellow (each row);

Actual result

• keyboard navigation - selects only first row then with TAB, it jumps over to the next checkbox;

Regression range

• regression range-wise, stumbled across builds that only selected the table and not the elements inside it; considering it as "good" to track the last changes in that area:
• last "good": 2018-10-14;
• first bad: 2018-10-15;
• Pushlog URL;

Additional notes

• reproducible with proton pref both on/off;
• setting as S4 from the get-go since this is really more of an edge-case;
• attached screenshot with the issue.

Maybe bug 1490366, which touched focus in richlistboxes?

When I focus the entire widget, I can arrow up and down through the rows and tab to get to the adjustment combobox.