On Androids 10+ system dialog is used when ENABLE or CHANGE button is pressed for folders selection and permissions.
That system dialog can be previously disabled by user or can be missing from some ROMs completely.
Please ensure, that following system app exists and is not disabled on your device (you may need to select some option to show all apps / system apps):
You can also restore that system dialog functionality by installing Files by Google app from Play (https://play.google.com/store/apps/details?id=com.google.android.apps.nbu.files&hl=en)
Package Disabler (and similar apps): If you're using Package Disabler or similar app, ensure critical system components (which disabler apps may mistakenly marks as "bloatware") are NOT disabled:
- External Storage (com.android.externalstorage)
- Files (com.google.android.documentsui)
- Media Storage (com.android.providers.media)
- Permission controller (com.google android.permissioncontroller)
If system dialog can't be restored due to any reason, you can use Settings / Misc / File Access Legacy Mode.