NetScaler isn't supported for any ASR flow and ASR in general I think needs to be across different regions also. And the 'move' capability Azure has for certain resources across subscriptions in same tenant has quite a few dependencies and limitations; definitely nothing I have tried for NetScaler for that. So maybe cross sub backup/restore. maybe. If you are talking single witnout any ALB stuff, etc. I haven't attempted that personally either. So probably be deploy of new appliance(s) and migrate config/re-license, etc. as best bet is my guess there especially if HA Pair needing load balancers and whatever else.