Thanks for letting us know, and welcome back from the dark side anytime you want 
Just a small update; WhatsApp works fine on aarch64, too; Sailfish 4.1.0.24 on XPeria 10 II.
The same problem with last version of Whatsapp :
Cannot restore.
I bypass this problem like this :
- Install whatsapp, don’t open it
- open Android options for whatsapp (menu → réglage)
- activate all permission fro whatsapp
- open whatsapp.
For me, restore work. (Sony XA)