Merging iPhoto Library on Hard drive to current iCloud Library - 42,000 items and 7,000

I have an iPhoto library on an external hard drive that has approx. 42,000 items and an iCloud photo library that is created on my phone and is around 7,000 items. The goal is to have both merged, and uploaded and active in the iCloud.

I think I should be able to switch my hard drive library to the systems library in order to switch it over to icloud and have them backed up in the cloud but this is not possible, I get a message saying "Not enough local storage, syncing paused."

So with my library being 204 gb, I am being told by Apple Customer Service, that I must have a device with enough local storage in order to use their back up services?? Is this the only way? To go purchase a iMac with 200 plus GB?

What about customers with libraries that want to convert to Apple... there is no option for them to bring their libraries with them?

I believe that importing would not work then as well, and would be insanely tedious and time consuming.

I will be cleaning up the library and my laptop to create space but there is no way I will come close to making this happen at this scale.

I had to find a way to store my photos long before iCloud was an option and now I feel stuck.

Is there a work around?

Goals:

Upload a large amount of items to iCloud from external hard drive

Use devices that I already own - iPhone 11 128gb, Mac Book Air 245gb, Hard drive 204gb

End goal - view travel memories on a photo frame or screen from a folder in iCloud that stays up to date, shuffles photos in home. WHY DOES THIS NOT EXIST!?

Any help and guidance is appreciated as I have been going in circles for weeks. Thank you in advance.