I use https://simplenote.com/ I was thinking about switching to a Foss alternative from fdroid but haven't yet. Works good for me.

I've been using Trilium Notes for the better part of two years and love it. I have used Obsidian and similar markdown apps, and I find it frustrating to add images due to the need to store them in a separate folder and reference them instead of just pasting them into the page and being done with it. To me, that's a barrier for notes when I'm trying to brainstorm. I really do like markdown, but it doesn't work with my though process.

I have a sync server setup at home (with no outside access) and do my main writing inside my network. For notes on the go I use the Notes app on my iphone (its quick and easy) and then drop the notes into Trilium when I get home.

Not exactly self-hosted but, I like UpNote a lot.

It's reasonably simple but, powerful enough for me, and it's fast & intuitive

Trilium. Tried a bunch but fell in love with this one. Others either didn't have support for inline math or weren't wysiwyg (Joplin). Also easy syncing between computers with its own server in docker, and it even doubles as a web version of the app.

I use Vscode with markdown preview, with a git repo. The only downside is that Windows incessantly wants to group instances of an application, so it's hard to keep my notes separate from my coding stuff.

Hypernotes. Work on every platform.

Link

I personally like Nextcloud notes for quick notes and nextcloud collectives for detailed stuff e.g revision. With nextcloud tables and deck it makes a great notion replacement

vimwiki

combined with some bash aliases, neovim config tweaks, and some bash scripts I've cobbled together over time. Then syncthing to share it across my laptop and desktop.

I've tried a few different note taking apps but I always find myself coming back to vimwiki. Its not the most feature rich 'app'. Matter of fact its pretty simplistic but I dont need or want most of the advanced features of other notetaking systems. But what it lacks in features, it makes up for by being a vim plugin. Seriously, I can't handle using non-neovim text editors/note taking apps. Having all of my neovim plugins, and other config tweaks make vimwiki the handsdown winner over the rest.

The missing vimwiki feature for me was a running "to do list" across all of my notes. So I wrote a script that got me the to-do list feature I needed.

I use Joplin mainly, but I've been trying QOwnNotes and Logseq out lately. All of them are pretty good imo

Zim.

Xed

It opens quickly

Notable. Cross platform (no mobile app), sync with cloud drive of your choice, markdown support, easy interface.

Ghostwriter and syncthing. Ghostwriter really has a good focus mode that really gets me in the right spot for writing. I use Markor if I am on Android and syncthing still works there as well.

VSCodium on the desktop, and Markor on Android. I write everything in markdown, and VSCodium is already where I spend half my time editing and writing code, so it was an easy choice. I also use Vim for quick one-offs, especially if I'm already working on a project with it.

Like others here, I also use Syncthing to keep my notes synced between home server, remote clients, and mobile devices.