Obsidian

I've used Obsidian for a couple years. It's a very good note-taking app. Vault (a paid add-on) makes syncing across devices effortless, but other cloud solutions also work. Composing in markdown's fast: your hands never leave the keyboard. It stores notes in markdown, so there's no lock-in: you can open them in a text editor. Once a note is synced to your device, you can reliably get to it even when you're offline. Quirks are in tables (a bit clunky) and the outline (hard to find on phones).

If you know, you know. Obsidian is possibly the best thing for keeping info that you'll ever try. It is for me. Incredibly generous program, and the mobile app is just as good. Used to be slow for me. I learned not to stack 1000's of mixed files (zips, exe's, full program folders) in your vault, and it's fine. much quicker now, on top of that.

Really, really good app! The slow startup speed is fixed now! Both, the desktop and the mobile apps start pretty fast. The only thing to improve, IMO, is the finicky "Send to" Obsidian on Android. It often reloads the app every time it's used, even if I just switched from the app (its battery settings are set to "no restrictions", so it shouldn't be killed). Another killer useful feature on mobile would be a quick note feature!