Installing Warpinator on RPI4 question

[otalado]

On a RPI4 (fresh install of Raspberry Pi OS 64 bit) with cinnamon desktop, I installed the Warpinator 1.4.6 (Flatpak) using the following steps:

sudo apt install flatpak
flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo
sudo flatpak install flathub org.x.Warpinator

At the end of installation of the Warpinator the following warning was issued:

Warning: Not exporting file org.x.Warpinator.appdata.xml of unsupported type.
(I don't know what that means, but I guess that this should not be a problem, as it is just the warning!?)

Warpinator is generally working, i.e. I can see the other PCs on the LAN, can send and receive the files, ... But there are two (rather annoying) issues with it:

• It doesn't show an icon in a tray even when that is checked in the settings
• It does not start on OS start even when that is checked in the settings

I tried work around

• Set the Warpinator to start with OS in the Cinnamon settings. That worked only if I set the Warpinator to start with main window open (unacceptable to me)
• Just put the Warpinator shortcut on the panel. That (kind of) works for me, but it is annoying.

BTW:

• on top of Warpinator main window there is the strop saying "Download folder not secure". So far I did not took time to understand what has to be done to secure it, but I believe that this is the cause for the issues I described above.
• I also have a disk with same OS and desktop as above, but with Warpinator 1.4.4 installed which works without a glitch. If there exists a way to get a flatpak for that version - that would be acceptable solution to me

I am looking for suggestions/help here as I do not want to report this as a bug, at least until I am reasonably sure that it is a bug indeed.