I use Syncthing to sync plain text notes between my PC and phone. I have a private syncthing relay running on my NAS so it’ll only sync when I’m connected to my home network. AFAIK, even if you’ve got global discovery on and are using the public relay network, your data is encrypted in transport.
It might come out on PC at some point in the future. IIRC Death Stranding 1 was PS4 exclusive for about half a year until the PC version came out.