I use emacs org mode (and emacs org node and emacs org agenda), and Orgzly Revived on Android (the latter can do DAV sync). It's quite nice and can do integration, search and quick capture, TODOs. It's also endlessly customizable--but I almost don't customize it.

Not FOSS, but check out Craft https://www.craft.do/

Trello: I could care less about open source or self hostable. It’s a tool

There is a Mac, Windows, Web, iOS, and Android app. Simple Kanban board like interface and I can add comments and descriptions in markdown for each entry.

I think there are some Workflowy clones that are OSS but I like the original.

I'm using NotePlan (https://noteplan.co) and loving it.

It's a macOS/iOS app (there's a somewhat limited Web version). IMO, the best balance between PKM and task manager/calendar management.

I've also tried Amplenote (https://amplenote.com) that has some of the features you want but the tagging concept lost me.

Excel / Google Spreadsheets?

Standard Notes.