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

This is a good starting point if you want to dive in.

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

YT plugin for Kodi is quite decent. Have it daily in use, no issues so far.

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.