First off, Notion is vastly superior to Evernote in every way (IMO). They have super streamlined apps for both Android and iOS, and the learning curve is negligible. Fully accessible in any browser, too. Once mastered, Notion is ridiculously powerful, and their free account ridiculously generous.
That being said, I recently discovered Obsidian, and although I have big love for Notion, I don't think I'll be using it anymore.
Obsidian also has apps, both for mobile and (native) desktop (Mac, Win, Linux), is open source (edit: my bad, not open source), and has a thriving plugin community on GitHub.
The learning curve is steeper, and Obsidian is one of those things that's so flexible that it's borderline overwhelming, but if you can wrap your head around how you want to use it, make it suit your needs, it's the absolute bee's knees.
Personally, I use Obsidian on my Mac desktop, and sync my Vaults (basically just a specific folder on your HDD containing your notes (individual markdown.md files) and folders) with Google Drive. I then sync the changes to my Android phone using Autosync for Google Drive, where I use the native Obsidian app, and Google Drive syncs to my Chromebook where I run the Obsidian Linux client.
I can't stress enough how much I love Obsidian, it's truly been one of my top 3 new software revelations in the last 5 years (Raycast and Midjourney being the other two). Highly recommended ❤️
Edit: Sorry, just now noticed this was posted in FOSS, so my suggestions might not be valid. Just thought since you're coming from Evernote, and there are fantastic, free alternatives, you might want to look into those 🙂 Both my recommendations have paid options (Obsidian offers paid sync, but is completely compatible with free alternatives), but both work amazingly without ever opening your wallet.