I don't test accessibility with a bluetooth keyboard with mobile devices very often. As you mentioned, I make sure the desktop browser works correctly with the keyboard and I test the desktop interface across various sizes. That can be done with the mobile emulator in browsers (ctrl+shift+M, from the main Firefox window or from Chrome's devtools) or you can see similar breakpoints if you bump up the font in the browser (ctrl++).
As long as the webpage is not doing anything unusual with the focus order, such as using
There are a few accessibility guidelines having to do with the keyboard:
- WCAG 2.1.1 Keyboard - All functionality of the content is operable through a keyboard interface
- WCAG 2.4.3 Focus Order - If a Web page can be navigated sequentially and the navigation sequences affect meaning or operation, focusable components receive focus in an order that preserves meaning and operability
- WCAG 2.4.7 Focus Visible - Any keyboard operable user interface has a mode of operation where the keyboard focus indicator is visible.
2.1.1 essentially says all the functionality of the website must be available to a keyboard user. That usually happens because all interactive elements (anything you can click on with a mouse) are keyboard accessible. But it is allowable to have a mouse-clickable element not be focusable with the keyboard as long as the function of that element is available to the keyboard user.
2.4.3 is often misinterpreted to mean that the tabbing order must be from left to right, top to bottom. While that's the ideal, it only becomes an accessibility issue if the tabbing order "doesn't make sense". That is, if the tab order affects the meaning or operation of the page, then it might fail 2.4.3.
2.4.7 says it must be visually clear where the keyboard focus is. If you don't have a custom focus indicator, then the browser takes care of that for you.
Now, with all the being said, you said "the tabbing is not effective or sequential". Can you elaborate what "not effective" means?
And by "not sequential", are you saying the tab order on the desktop is in a different order than the tab order on the mobile browser? That would be odd. I have not run across that.
If you have a public URL, I can try it out.