There's a merged pull request on the void-packages repository

owncloudclient: update to 5.2.1.
https://github.com/void-linux/void-packages/pull/47025

Description:
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#### Testing the changes
- I tested the changes in this PR: **briefly**

I've been using 5.0.0 for a while, and now updated to 5.1.0.

Note that kde integration (#45352) has been removed.
There is an external project: https://github.com/owncloud/client-desktop-shell-integration-dolphin but I don't use kde and I wouldn't be able to test at all.

It was necessary to build `qtkeychain-qt6` which I copied with obvious changes from `qtkeychain-qt5`. Should this new pkg keep @yopito as maintainer?

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