What is Reddit's opinion of Minder?
From 3.5 billion Reddit comments

➔ Minder website

By popularity on Reddit, this Service is:

#29 in Mind Mapping apps

3 reviews of this app found across Reddit:

which distribution are you running? is this the program you are trying to install? https://github.com/phase1geo/Minder

if so, how did you try and install it? what commands did you run?

from the output you posted, it does appear that you may have libgranite6 installed. you should be able to verify/check with apt list 'libgranite*'.

Not KDE, but there's one for Elementary and a rather basic mindmap from Markdown that you can export to SVG, thus you can edit it afterwards with Inkscape, Karbon or something else

There are instructions on the GitHub page you linked: https://github.com/phase1geo/Minder/blob/master/README.md#installation

Install the required dependencies through eopkg and then follow the build instructions.