Not sure about the self-host part but Jabref and Zotero might fit.

What are the reasons for the Pi Hole to Adguatd switch?

It’s trillan you are talking about. I am old too :D

I love it so much that I put it right away on my donations list.

Using Argon NEO and quite like it. In my case it was important to have the ability to use a HAT (HiFiBerry).

You probably mean Radicale. Baikal is an option too.