Acknowledging you want a web-app browser based alternative and this won’t answer your question, feel free to ignore.
But as for general notion alternatives, and actually if you prefer to go in the other direction away from web based—Hands down would recommend Obsidian.md above any other open source alternative.
While it's not 100% "batteries included" like proprietary apps (though this gap has narrowed considerably), Obsidian truly shines if you're even slightly inclined toward customization. It's "hackable to the core" — you can build practically anything on top of it, which satisfies open source purists. Yet for practical users not looking to build their own software, Obsidian still punches above its weight — it's highly functional and polished out of the box, requiring zero setup to be immediately productive.
The integrated community plugins library lets you extend vanilla Obsidian to match most proprietary software, including Notion's "databases" functionality (arguably Notion's best feature), LLM integration, and much more. Since these plugins are themselves open source, they too can be customized beyond their original design. It's the perfect blend of freedom with valuable functionality either built-in or one click away.
What initially drove me from Notion to Obsidian wasn't the customization aspect, but the need for local storage and non-cloud syncing for sensitive data. It's egregious that Notion still doesn't support this outside their Enterprise license. I almost overlooked this by simply not using Notion for sensitive data, but the final straw came when I lost access during Notion's service outages. Even though these were infrequent and brief, being unable to access my data when needed was unacceptable. Arguing with devs about local storage and offline functionality only to face that situation made me realize how absurd it was that Notion doesn't even provide a cached version when offline. Without internet, Notion is essentially a brick — your data exists somewhere in the aether, just not on your device. That's bananas.
After switching to Obsidian and solving the local storage "problem" in 30 seconds, I gradually discovered more functionality and have since customized it as my central organization and research tool. Couldn't recommend it more highly.
I'll stop my rant now — Obsidian speaks for itself and doesn't need my endorsement, just as Notion's shortcomings are equally well-established.
Obsidian is on a fundamental level a very different app to Notion (you already mentioned the web app, databases, ...). It is also not even close to being "hackable to the core", it is not open source. That title belongs to Emacs.
But as for general notion alternatives, and actually if you prefer to go in the other direction away from web based—Hands down would recommend Obsidian.md above any other open source alternative.
While it's not 100% "batteries included" like proprietary apps (though this gap has narrowed considerably), Obsidian truly shines if you're even slightly inclined toward customization. It's "hackable to the core" — you can build practically anything on top of it, which satisfies open source purists. Yet for practical users not looking to build their own software, Obsidian still punches above its weight — it's highly functional and polished out of the box, requiring zero setup to be immediately productive.
The integrated community plugins library lets you extend vanilla Obsidian to match most proprietary software, including Notion's "databases" functionality (arguably Notion's best feature), LLM integration, and much more. Since these plugins are themselves open source, they too can be customized beyond their original design. It's the perfect blend of freedom with valuable functionality either built-in or one click away.
What initially drove me from Notion to Obsidian wasn't the customization aspect, but the need for local storage and non-cloud syncing for sensitive data. It's egregious that Notion still doesn't support this outside their Enterprise license. I almost overlooked this by simply not using Notion for sensitive data, but the final straw came when I lost access during Notion's service outages. Even though these were infrequent and brief, being unable to access my data when needed was unacceptable. Arguing with devs about local storage and offline functionality only to face that situation made me realize how absurd it was that Notion doesn't even provide a cached version when offline. Without internet, Notion is essentially a brick — your data exists somewhere in the aether, just not on your device. That's bananas.
After switching to Obsidian and solving the local storage "problem" in 30 seconds, I gradually discovered more functionality and have since customized it as my central organization and research tool. Couldn't recommend it more highly.
I'll stop my rant now — Obsidian speaks for itself and doesn't need my endorsement, just as Notion's shortcomings are equally well-established.