Hello,
I have just posted a $200 (USD) bounty over at:
https://bugs.kde.org/show_bug.cgi?id=435001
I will be happy to release it once a patch has been merged into KDE Neon Unstable and I can verify it working.
I know that this is a bit of a niche bug but I think that any type of bug that leads to data loss (even a “minor” one such as loss of the user generated xattrs in this scenario) requires a fix.
Happy to answer any questions regarding the bug and/or the bounty.
Hello 
I have opened a merge request to address this issue for you, and posted a follow up question in the linked bug report to ensure I am covering all the situations where this issue arises.
I have added some extra things to test for at the bug report. That’s very exciting! 
Update: the fix has been merged into master, so you’ll be able to test it out as soon as Neon Unstable has published it.
It doesn’t seem to be built for KDE Neon yet for some reason, but it is available in the flatpak nightlies.
flatpak install --user --or-update https://cdn.kde.org/flatpak/ark-nightly/org.kde.ark.flatpakref
flatpak run org.kde.ark
or right-click an archive and choose Open With → (Nightly) Ark
I have tested this with the flatpak Nightly and it works great! Thank you for your efforts!
Please let me know in an email or PM how you would like me to make the bounty payment. Cheers!
That’s great to hear! I will send you a PM