Exotic non-essential function that nobody really uses and tests?

Yep. Have never used it. In general I don't like the idea of clicking external links in programs that want to connect me to gawd-knows-what.

why didn't they at the same time fix synaptic to receive them over https?

Same reason they  left it unable to use the new .sources format when they shipped Trixie, they care about their users, it says so in their policies they like to quote so often...

Package libxapian30 is not installed.

Then sudo apt install libxapian30 and since the system is borked from trying to install the -dev package sudo dpkg -r --purge synaptic-build-deps you may want to do that first. This is why I dislike those GUI programs they do nothing to show you how the system works and leaves you unable to solve even the most basic of problems due to this lack of eperience.

i just have the website bookmarked for easy access:

https://screenshots.debian.net/

i seem to recall breaking synaptic a few years ago(wouldn't start/display/etc), and i just did a fresh install to make sure all was back to normal(as normal as it gets...ha!)

BTW: the same problem already exists on Daedalus. Same as Excalibur. When I ask for a screenshot of a package, I get a square window with a small terminal-like icon. Thats it.