Gyroplast

Delete the existing file /usr/share/icons/bloom/icon-theme.cache, install the package normally without forcing, and don’t sweat it. That cache can (and should automatically) be recreated afterwards with gtk4-update-icon-cache /usr/share/icons/bloom, but it’s strictly not critical.

The previous version of the package did not include this file, lending credibility to the assumption of a packaging mistake, as does the existence of an issue for that problem already.

Just fix this nag yourself as described, and expect this to be fixed by the packager eventually.

What kind of soulless psychopath leaves a window of this size unmaximized is the real question here. Also, a horizontal scrollbar in the main section, able to scroll maybe 8 pixels total to see some more of the glorious empty padding, could have been a nice touch as a consequence of the “unintended” window size.