Request #87267 has been Accepted by DeepChirp [1]: Original author agreed to deletion:
> There is a pending deletion request for this package. I would be ok with this request being accepted. I will _not_ bring this package back as `syncthingtray-qt5`, though. It will simply stay deleted. Nothing speaks against using `syncthingtray-qt6` at this point and the Qt 5 build is no longer needed by users. [1] https://aur.archlinux.org/account/DeepChirp/
