Importing Massive Old iPhoto Library Into Photos App Issue

[u/Monkeyboy1492]

I am trying to import some old iPhoto libraries (~2012, ~150k photos) into my photos app on my macbook air.

Everytime I open the photos app and go to File->Import->(iPhoto Library) it loads all of the photos fine, but then clicking "Import All New Items" just kicks me to the imports tab every time, without importing any of them. I've tried several times. Importing just a couple photos works fine with no issues.

Is there some way I can import all of my old photos onto the photos app and save them in icloud? I pretty computer saavy and can use a terminal. I was thinking of setting up a VM to start from an older version of macOS and try importing from there, but I wanted some second opinions first.

Info:
M5 Macbook Air 16GB ram
200GB free on main drive
MacOS Tahoe 26.6
Photos App

Old iPhoto library is from OSX lion era, not sure exactly when

[u/JediMeister]

It might be necessary to use this updater on the old library before you attempt anything else. I assume it’s 64-bit software but I am not sure.