Kstars did complete. It's running now.
GSC is just for simulator camera. Good for troubleshooting, but not critical.

Well that was easy!

Now you know how to build KStars (and family) when you upgrade to a faster single board computer, like an ODroid N2+, for example.

Yes GCS can be skipped. You need it only to get stars when using simulators. Otherwise it is no needed.

Yes. But I still want it.

I had a little time to look into this. It isn't trying to build GSC. That's already complete. It's trying to build the next thing in the list, which is PHD2. And it tries to install libwxgtk3.0-dev in preparation for building PHD2.

Modify the apt-get around line 896 in the script, and change it to the new updated package name, and try that.

I understand why it might look like that to you as I only shared a small excerpt from the terminal as it was running the script. But I can assure you it is indicative of GSC not being compiled. I believe it says GSC is already installed due to it having been present before the upgrade to Bullseye, and the fact that the images produced by the simulator are currently corrupted.
And I also see no new build directory for GSC. Furthermore I saw PHD2 compile properly, and it runs fine.
Maybe there are also some other things I need to clean up first.

In a way we are both right. The script is skipping the build of GSC because it thinks it's already installed. Delete the /usr/share/GSC folder to force it to rebuild GSC.

GSC does not depend on the wxgtk library. That is strictly for PHD2. The fact that you manually installed the necessary library is probably why PHD2 built fine, even though the script complains about missing the wxgtk library. I'd still update the script as I mentioned.

Thanks. I believe you are correct. Going to work on it some more later.
Now, I just hope PHD2 is ok.