An alternative is to use Git(hub) as the mediator, and here Orgzly is a decent Android app with Git support[1]. It just has a tendency of clobbering your git log with automatically generated commit messages. It has WebDav capabilities too, so you could use Nextcloud as the mediator instead.
There's also Syncthing, which is probably what everyone wants: all devices haves the same info, you commit to VC what you want when you want.
My personal workflow? Accept that my desktop is where I do the real planning, and that the mobile is just for quickly looking up stuff in my notes. If I have ideas, I can email them to myself and process them later when I'm back on my desktop. Is it perfect? Far from it. Does it work? yes.
Alternatively: how about something like this:
- Stick the org source files in a private <Syncthing, or Dropbox, or equivalent> folder, so you can privately sync across devices.
- Use a file watcher to auto-export selected files to a shared version of the folder so you can share rendered content with others, with permissions. pandoc is an option but it doesn't export all of org. I think it's not a crazy idea to use Emacs itself as your command-line exporter. If you want special org sauce in the export, maybe pass the command line invocation a dedicated init file for export-only use.
- Further, because you are familiar with git, it may be not-crazy to run a Github/Gitlab/daemonised "render" action, on push to a remote repo. Once again, using the Emacs binary as the full-blown exporter.
I also have another set of notes that I sync with my phone and laptop via Syncthing, but that stuff isn't really using the more interesting org features, just quick and dirty notes. For anything serious it's just git.
I regularly access and update my notes on at least 5 different devices, and I often need to share notes with non-technical people, where the barrier of entry needs to be nothing more than a single link they can click. Currently, Google Docs serves that need, but it's not ideal for writing.
The ideal solution for me would support using a Git service as the backing store, but the churn of making commits to synchronize has to not get in the way.