KDE's portal-kde and firefox is nice first steps but so far it doesn't work properly. Try to download some file(for example ZIP file here https://github.com/artistCDMJ/ez_paint) 1) It says it will download file and give it a name. However once you actually want to save it the filename is lost, you have to type it yourself. 2) If you don't specify file extension and it recognized that the file you're saving is ZIP(for example) it saves the file with "[zZ][iI][pP]" extension instead of "zip". I don't if its related to 388090 bug.
Hi, both KDE and Qt dialogs do not support Gtk's advanced filters, where they can set regular expressions, like the one you mentioned, which results into this weird file naming. There is nothing wrong about this in portals and I don't really want to write workarounds for that. They support this because their file dialogs are case insensitive (regarding file suffixes) so that's probably why KDE/Qt file dialogs don't support this.
I don't want to write workarounds, but it looks I will have to as this is probably the only way to make it work.
*** This bug has been marked as a duplicate of bug 399889 ***
Proposed workaround: https://phabricator.kde.org/D17677