It has been years since I was involved with this company, but at the time I worked there, Mylio was very much concerned with this problem, and a brief look at the FAQ suggests that the goals have not changed: https://mylio.com/. - Source: Hacker News / 9 months ago

This is an issue for YEARS in icloud. Apples cloud is a mess since me.com... I also had a huge (about 2.5TB) photos library. I switched to mylio.com - in general its a great alternative. Source: 12 months ago

Does it have to be OSS and free? Otherwise Mylio might be the way. Source: over 1 year ago

I use mylio https://mylio.com/ and have been very happy with its cross device and platform sync and backup in conjunction with my QNAP NAS. Source: over 1 year ago

Now, if you also have a PC and want to keep , say, 20 thousand DLSR or Mirrorless camera photos along with smartphone photos, a tool called Mylio syncs photos peer-to-peer (no cloud) across devices. It has some decent editing functionality (tagging, rating, keywords, albums) if that matters. https://mylio.com. Source: over 1 year ago

They have linked the unofficial version in their GitHub repo https://github.com/linuxmint/warpinator. Source: about 1 year ago

You can then use Syncthing or Warpinator alongside it to sync them to other devices. Source: over 1 year ago

Other than those you mentioned, there is Warpinator. It works flawlessly for me. You need to create a hotspot manually if there is no internet. Source: over 1 year ago

[Warpinator](https://github.com/linuxmint/warpinator) will do this. I've used it in the past and I just double checked if it will send android to android, which it does. There are packages for Windows and in F-Droid. It is developed by the Linux Mint team, so seems like a trusty source. But, always double check if you are confident in the publisher. Source: over 1 year ago

I use Warpinator. It is developed by Linux Mint but I have ports installed on Windows, Android and even iPad. Source: over 1 year ago