Resilio Sync: use it in backup mode to sync photos to your desktop pc/mac/nas. Delete photos from phone when you want to free space. Also lets you access and edit normal files, either on demand or by sync. https://play.google.com/store/apps/details?id=com.resilio.sy...
PhotoSync: sync your photos to pretty much anything. https://www.photosync-app.com/home.html
Termux, ssh and rsync. Thats it. It works. I tell my phone, try to rsync when its been charging for at least 5 minutes and its evening time. Hurray.
Whereas the rsync method is exactly this: "syncphone" on my main machine. If it doesn't connect, nudge the phone so it wakes up (it'll connect anyway eventually; the phone seems to wake up on its own now and then). And then it's all automatic and scriptable from that point. I realize that perhaps 0.1% of smartphone users have the skills to automate things at that level and therefore care.
The auto rsync when charging is a good idea. I guess Termux can still get access to the battery/charge state?
Another example of user hostility: While on Android phones, at least older ones, bulk transfer of files via USB to/from a Linux machine has always been hit and miss, it's been rock solid on iDevices. Just do "idevicepair" and after that, transfer away to your heart's content, fast and solid. Only now I read that the latest version of IOS may have messed that up too, in the name of security of course.
Not sure that's what's causing it; I can definitely scp files from my Android phone's SDCard to my servers. But I've not tried initiating the scp from the other machine to my phone.
Anyway what's left of filesystem access for Termux isn't really a blacklist as in "you're forbidden to go here" but rather feels like a whitelist. There are a few carefully selected places you're still allowed to go, front and center being the DCIM directory.
Certainly, when I unlocked a Sony Xperia XA2 it did something similar where it won't ever get OEM updates ever again.
With ssh-copy-id it takes a single command (1-line script) to rsync the phone's DCIM directory to my main machine for further processing. Nothing needs to be done on the phone at all other than to lightly nudge it to wake it up so sshd sees the connection attempt.
Downside: Android security clampdowns mean termux can't see the SD card. So I can only sync down the phone's internal camera directory and that's where I have to store the new pictures and videos. This means space occasionally runs low and I have to move stuff to the SD card. But in the future, they probably won't allow Termux to even work any more in its current form - no "exec" of executables that werent' installed as part of the apk.
Why do all this? Because I'm old school. My phone is an extension of my data ecosystem, which lives on (redundant and backed-up) hard disks in my home computing setup. I don't even let the phone sync the photos to the cloud.
Admittedly I've found no other practical uses for it; all the interesting stuff is blocked by Android security (e.g. back up or otherwise process your call/SMS history).