There is hope for "Open with list" on flatpak package- please see this !
Hi. This issue on behalf of discussion that was made within #20 (closed)
It seem that it is quit possible to make the new feature of [making PDF Mix Tool appear within "Open with list" of right click], that you already disabled on flatpak by commit 98a2f76f, it is quit possible to make it active on flatpack package also !
I tested other flatpak application called pdfslicer & it appeared within "Open with list" - see the following screenshot:
Please notice it is not necessary to make it directly appearing within this list. There is option in "Open with list" called "Other application". It is quit suitable if user can use "Other application" sub-option of "Open with list" of right click, to brows & manipulate needed application.
pdfslicer is a fron-end for QPDF & it utilize no other front-end .....
Please see this issue carefully.
Thank you too much for your very hard efforts & patient!