Steps to reproduce the issue

Use a form with a field of custom type that extends JFormFieldCombo.
Its getOptions() method is returning a list of items.

Expected result

When you click on this field, the list of items is proposed.
While you enter caracters, this list is filtered based on the caracters already typed-in.

Actual result

It works on PC, but not on (at least Android) smartphone.

System information (as much as possible)

Joomla 3.9.10

Additional comments

As stated here, keyCode on Android does not really reflect the exact keyboard key pressed.
https://bugs.chromium.org/p/chromium/issues/detail?id=118639

As a fix, I loaded another JS file, that the one automatically loaded by Joomla (/media/system/js/combobox.js)
and changed in it:
line 145 :
if ((keycode > 47 && keycode < 59) || (keycode > 62 && keycode < 127) || keycode == 32 || keycode == 8)
with
if ((keycode > 47 && keycode < 59) || (keycode > 62 && keycode < 127) || keycode == 32 || keycode == 8 || keycode == 229)
as keyCode was always 229 on different Androir smartphone and browsers while typing on the keyboard.