It is unclear what the user needs to do to install this on mac. All instructions for downloading seem to be for calligra generally, not the planner, and are also seemingly out of date? According to https://userbase.kde.org/Calligra/Download#Mac_OS_X ... I need to use homebrew to install [this tap](https://github.com/adymo/homebrew-kde) whose most recent commit is 7 years ago and unsurprisingly does not work. The instructions don't even say what formula I'm supposed to install. Also I'm not sure I understand what krita has to do with anything. Anyways I'm trying to install the planner on mac by any means. If I need to build from source I will, and I would appreciate some guidance, but you may want to update the documentation cause it's probably sending more people on a goose chase.
I am afraid the doc is out of date. Krita separated from Calligra some years ago, see krita.org. Plan is released separately for practical reasons. It just became too much work to keep it in sync. My knowledge of mac is a big zero, so... The current release does not compile on mac. The current development version does compile on mac, see https://binary-factory.kde.org/job/CalligraPlan_Nightly_macos/ (Don't be confused if you find https://binary-factory.kde.org/job/CalligraPlan_Release_macos/ atm it is the same as the nightly build, a CI issue) I do not know if anybody has tested it.
If you want to build yourself, I would try craft first: https://community.kde.org/Craft I did this for windows and it worked fine. You can also get help on: IRC: https://web.libera.chat/?channels=#kde-craft and the mailing list: kde-windows@kde.org (don't be put off by the name it's used for mac too)