I've been using Zettle Notes with syncthing for a few years now. It syncs with my laptop as just a directory of markdown files that I also edit with Vim (plenty of good plugins like Vim wiki).

I've never used it, but I've heard good things about Notesnook.

Joplin. I use it on my phone, multiple laptops and Linux desktops.

Currently using siyuan. Just wish you could use the app with a self hosted instance.

Actually, you can use Signal for this, if you have it on both your phone and laptop, and use "note to self." I prefer this because it's very straightforward and isn't bogged down with a lot of extraneous extra features that other notetaking apps I've tried tend to have.

https://silverbullet.md/

It's like obsidian (I hear) but FOSS. I love it and it's by far the self hosted service I use most.

It stores your notes in a plain directory hierarchy of markdown files so you can just point a cron shell script at it to git add/commit/push at your desired internal and you've got history tracking/backups too

Edit: also provides a PWA so you can "install" it on your phone instead of always using a full browser.

Edit x2: includes a Lua interpreter so you can get scripty with it. I use that functionality more than I expected and I suck at Lua

Edit x3: and it auto synchs to each device when open with conflict detection. Full copy is stored local to each device, synched when possible

I’ve been using a self-hosted Jotty instance, it’s been pretty great!

https://jotty.page/

I'm using Logseq and it's the least bad of the FOSS options I tried so far.

obsidian is not FOSS BTW

Joplin can sync between phone and laptop with a number of network storage options

https://joplinapp.org/help/apps/sync/

or you can self-host Joplin server.

https://github.com/laurent22/joplin/blob/dev/packages/server/README.md

You can self host Anytype. It looks like notion, but is FOSS and total under your control.

notesnook

I use Joplin through some WebDAV with my cloud provider, kDrive.

Works perfectly once set up.

I don’t know if you could make it work directly from your phone to your computer though.

Is there something wrong with Standard Notes that I should be aware of? It hasn't been mentioned here. It has the AES-256 encryption standard, there is a free tier, it's open source and it undergoes regular security audits.

Obsidian + Syncthing has been working prefectly for several years now for me, across Windows, Android and Linux.

Could look into self hosting an Obsidian Sync server, see this blog:
https://pinggy.io/blog/self_hosting_obsidian/

Obsidian - https://obsidian.md/

edit: And you can obviously do it without pinggy's tunnel for remote access.

not (completely) open source but signal has a "note to self" function i use for that

Notesnook should do it! It has a premium monthly subscription thing that gives you some extra functionality, but the free version does sync automatically between devices. I've been using it for a year now myself and have had no complaints.

Anytype is nice.

I found the best option markdown on my pc and a notepad outside.

I've set up Joplin with Syncthing and it's been working for me.

Syncthing and Org Mode.

I am currently in the process of migrating my Google Keep notes over to a self hosted instance of La Suite Docs. It sounds like a big Google Docs alternative, but feels way more like a notes app.