Photos in MacBook does not sync through iPhone hotspot

I am on holidays without regular access to Wifi but always have access to a mobile data plan though an iPhone hotspot. I have an older MacBook that I can't upgrade past Big Sur. I know how to toggle on/off low data mode in the iPhone 7. The MacBook works really well through the hotspot except for the one main app I need it for - iCloud sync in the Photos app.

I see others have this problem (While I am using Personal Hotspot my Phot… - Apple Community and Photos cannot sync while I am connected t… - Apple Community) but no solution. This seems to be a design fault - these other posts say that the Mac will sync photos using an android phone but that same SIM card in an iPhone won't sync photos.

Has this issue been fixed in more recent MacOS versions, and is there any way to fix it in Big Sur? The only solution I have found is creating a VPN which is beyond me (I use Apple devices to keep things simple!).