I think I have understood a procedure to do what you ask!
1) Import/Add photos to Lightroom on any mobile device (Android, iPhone, iPad, Lightroom-Desktop on a PC or Mac) (Note your 20GB limit)
2) Set Lightroom-CLASSIC to [Sync] (after setting the Preferences for the Lightroom Sync Download Folder location!)
3) Only when ALL photos have (automatically) downloaded to Lightroom-Classic folders- goto next step:
4) Delete the photos in [All Synced Photographs]. (The downloaded files will remain in the downloaded folders)
And you can find a similar discussion here- where @JohanElzenga suggests adding the photos back to the Adobe Cloud (as Proxy files that don't use any Cloud space!)
Regards. My System: Lr-Classic 12.3 Photoshop 24.3, ACR 15.3, Lightroom 6.3, Lr-iOS 8.0.8, Bridge 13.0.3, Windows-11.