I am a long time LR user, but not an expert. I use LR to manage 5 family iPhones, on Nikon full frame. 110,000 files in my library.
BUT, I've had a long standing problem when importing from our iPhones. There are A LOT of junk images on our iphones, pics of receipts, screenshots, pics of cars my son can't afford.... Let's ballpark these junk images at 90% of them, or 20,000+ images.
I do not need to import these, nor do I want them taking up space in the catalog.
How can I tell LR, on import, "mark these as not needing import" or these were imported, but then deleted....don't bring them in again. In fact, don't even show them to me on the import NEW screen.
When I am importing from each family member's iPhone, the first 5000+ photos shown are years old, and not needing attention or import.
This seems like a funtion that should already exist.
Create a separate folder on a hard drive to place the junk photos in. It can be any hard drive, perhaps a external one.
Import the junk photos in LrC.
That way, LrC will see them as previously imported.
Now, a few additional points
When using LrC for normal use, that hard drive does not need to be connected. This could be an old external hard drive that you have laying around.
You can delete the library previews for those photos to save space.
'You might be able to delete those photos outside of LrC to save space, but do not remove from catalog, and put up with the error notice that the originals are missing, but, I do not know if that might degrade the catalogs integrity,
Another way, offload those junk images from the source.