https://github.com/libimobiledevice/ifuse
I type "ifuse /mnt/iphone" and there is a DCIM/###APPLE dir with the images and videos where I use "cp -a" to copy the files to my computer
If you want a certain format for the images, just set the camera to use that format, or convert it yourself after copying off the phone.
My process is:
* Connect iPhone to MacBook or similar
* Use Image Capture to dump all photos to a local directory in $HOME
* rsync the directory to my NAS
* Run a wrapper script around ExifTool [0] to sort the photos into folders
I have done it this way since forever.
Everything has always transferred off just fine at least for me.
For a huge library like that I would go with a reliable software like iMazing.