I use 2 giant plain-text files.
One for notes. The other for to-dos.
I use git to sync to a private git repo using my own app https://github.com/tanin47/git-notes (work with Mac, windows, Linux)
My priority is that I want my notes to live forever. Using GitHub seems to achieve that purpose. (I used many notes app before which I threw away when moving to a new app)
It's just important to have automated triggers to push and pull things to avoid conflicts. That's possible with Shortcuts on iOS and there's a git-plugin for Obsidian as well.
Using text files for notes is meh. I've just been pointed at Bear app, and using tags to manage grouping specific notes has been really nice.
It's all stored as markdown, so you can go in and edit the page. nb also syncs automatically every time a note is edited.
Images, pdfs, docs, etc. can all be dumped into nb.
On mobile, I use gitjournal, and point it to the same gitlab repository, so the same notes are synced on mobile.
The notational-fzf vim plugin (https://github.com/alok/notational-fzf-vim) is excellent for searching notes and just works if you point it to your .nb root directory.
The next best thing is notable (https://notable.app/), which provides a much better interface, but doesn't do the download url thing. Gitjournal and notational-fzf also work with notable.
Its a 10 LOC bash script on each OS, it allows me to keep all my notes in markdown format, and use whatever markdown editor I want.
It allows me to sync any kind of content, not only notes, but also images, jupyter notebooks, whatever I want.
As a MD editor i tend to use Typora, but I might use VS Code, emacs, etc. depending on what i am doing.
I use about ~3 machines in total for work and personal time, and this works seamlessly across all of them. It allows me to keep my work notes separate from my personal notes, and e.g. keep them in our work's git servers.