Org-mobile exists[0], but I have yet to meet anyone actually using this protocol in the wild, and requires you to have your own server to mediate from, as well as emacs running on your phone.
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.