Hi meowist,
You did say "Any suggestions welcome."
So although I do not know a quick way to just import the 100,000 photos to your Mac,
several ideas come to mind ... please excuse if these ideas are surplus to requirements.
We can not know your level of expertise, and the preparations you have made for the task,
or how much free storage is available on your Mac, or the memory available for the task.
At the least, we may begin a discussion, that those with expertise may choose to join.
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Wondering if your Mac has enough memory / storage space free for the photos you want to import, and sync with iCloud.
How to: See used and available storage space on your Mac – Apple Support
And: Find out how much iCloud storage you need for your Photos Library on your Mac - Apple Support
How to: Check your iCloud storage on any device – Apple Support
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If necessary: you may need to "optimise" the photo storage on Mac.
Eg: Online (non-Apple) article below:
How to load a massive amount of data into Photos on a Mac set to Optimize Mac Storage
https://www.macworld.com/article/233281/how-to-load-a-massive-amount-of-data-into-photos-on-a-mac-set-to-optimize-mac-storage.html
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Wondering too, if you may want to import/ and / or / keep a back-up of all your photos for the safety of your large photo collection. Apple seems to recommend we do this. (ie: Deleting synced files either on Mac, or on iCloud, deletes them from the other synced storage.)
An idea: Would it be be easier to download everything to an external hard drive with plenty of storage space. You could then transfer the photos to Mac at your leisure, or as needed, while keeping a back-up of all photos at hand.
Eg: Connect and use other storage devices with Mac - Apple Support
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If needed:
MacBook Pro Support Team:
MacBook Pro - Official Apple Support
Cloud Support
iCloud - Official Apple Support
All the best :-)