If windows or android is a must then use something that has a client in them. I use OneDrive because it's the cheapest in my region. It's got terrible support from Microsoft, just lazy and terrible, but there are third party sync solutions for all platforms.
I think GitHub/gitlab issues is totally viable. Obsidian/Logseq too.
If it doesn't, you just need to find one that does. I use it because I don't care about iOS. If you need one that supports iOS, macos, windows, Android and Linux and there isn't one, then it's justified to pay for their sync solution.
I think GitHub/gitlab issues is totally viable. Obsidian/Logseq too.