Did you click the third link I posted, which searches Flathub for KmCaster only to come up dry? This was point (c): You have to trust that their search engine is correct, maintained, and updated. That doesn't come for free, it takes effort, and things go wrong.
[0] https://flathub.org/apps/com.whitemagicsoftware.kmcaster
https://github.com/flathub/com.whitemagicsoftware.kmcaster?t...
Also, the image on that page is outdated, which would have been one more thing to maintain. In addition, the install instructions are four lines of code to run, compared with three lines of code to download without Flathub. My point stands: Flathub adds an unnecessary maintenance burden (to some projects).
https://flathub.org/apps/com.whitemagicsoftware.kmcaster
https://github.com/flathub/com.whitemagicsoftware.kmcaster/p...