How about Syncthing? It keeps directories synchronized in multiple devices, and works both over Wi-fi or regular internet. You can set directories on read-only or send-only modes to suit your needs. It work for Mac as well.
The way i transfer files from pc to phone is with riot messenger, i made an account for windows desktop and send it to the riot app on phone, + works from phone to pc.( you can delete the content from riot after its been transfered)
Anotherway I like is a program called Onionshare for very large files which is for linux, mac, windows if u want to transfer to your phone or send to anyone else, it turns your pc into a file server without having to upload anything, drag and drop the file, and it generates a tor link for tor browser as a download.
perhaps these are a bit cumbersome methods but works for me.