DocumentsUI, the AOSP standard "file manager" is quite buggy here (I use Lineage 15.1), especially in the context of multi-user and work profile (meaning it does not show files for other users then the main user and is hence not usable).
For "simple" file browsing, I therefore substituted DocumentsUI app (
com.simplemobiletools.filemanager.pro which works much better.
My issue and the core of the question is, that the glorious "facebook" WhatsApp Manager when attempting to attach files, resorts to opening the intent specifically for
com.android.documentsui and fails even to open
com.simplemobiletools.filemanager.pro even in the case that it is the only filemanager still installed. Hence I cannot attach files in other users in Whatsapp, due to the buggy DocumentsUI and WhatsApp not being willing/capable/well-enough-designed to make a general "FileOpen" intent, instead of referring directly to
I understand that WhatsApp is particularly made very little IT-able persons, who do not care about privacy very much, therefore it is clear that the WhatApp is not geared to allow/accomodate for educated and more able users which might desire to use not the standard
An answer to this question would be to provide an insight which
com.android.documentsui would be able to integrate well with WhatsApp Messenger