I kind of love note taking apps so I can rundown a few:

• Logseq (FOSS, can technically run in a browser but it’s very limited and literally called “demo”)
• Obsidian (not FOSS but local md first, very mature and a huge community)
• Joplin (FOSS and probably general go-to for cross-platform open source notes in general but is a bit of a memory hog)
• StandardNotes (you already described this one)
• notesnook (very new offering probably most similar to SN but I don’t know)
• AnyType (also very new and striving for more of a Notion-like experience but I think still needs time to mature)

I use Logseq most often, although I prefer Joplin on mobile. Obsidian and Logseq are more “personal knowledge management” and may be overkill for simple note-taking, plus I feel they are a little bloated on mobile. Honestly not sure which ones work in a browser, but I agree that’s a feature I’d like more of. All of these though I believe are cross-platform so should be usable on mobile or desktop.

I personally use Notesnook. It's E2E, Open Soure and Cross Platform.

I've used Joplin for a while and it's solid.

Obsidian here.

idk maybe notesnook?

This video is pretty funny and gives some good ones

I enjoy notesnook. Free, Foss, e2ee, with cloud sync. Available on izzyondroid and fdroid.

Notesnook for sure. I really disliked Joplin. Particularly the Android app. Just really poorly designed.

Acreom promise but it's new enough they don't have E2EE or even local only on mobile. Both are on the road map. Dev seems engaged and cool though.

Edit: I didn't see the open source req, acreom isn't. But it's still a cool app. And I'd they can get local only on mobile, then you can sync however you want as it's just flat Markdown, similar to Obsidian.

I've been enjoying "Anytype"

I use Org Mode and Org Roam in Doom Emacs.

You're putting yourself in a tough position by asking for both E2EE and the ability to use from a browser. You have to trust the web app each time you open the page, and hope that they haven't altered the deal to simply grab your data after it's been decrypted by your password. I have no idea how likely it is that Standard Notes would do that but I'd reconsider the browser requirement specifically if E2EE is non-negotiable for you - an offline open source client program would be a much stronger position.

For my money, I use local text files and SyncThing but it's probably not spiffy enough for many people/purposes.

Maybe https://dillinger.io/ as a self-hosted raspberrypi docker instance? And instead of saving to public cloud services just export the markdown file as local pdf.

On mobile I can't just find pdf export button like on desktop.

not e2ee but I use Nextcloud Notes

Simplenotes works in a browser, plus there is an app for mobile.

Joplin is great an encrypts everything (if you want). You can host the synced notes yourself and you can install a web frontend if you're into such a thing. I use it on mobile, windows and Linux where it works great

Standard notes seemed fine for a non syncing app. I think it's the syncing features everyone has issues with.