I bought Zenfone 9 from US (C version) and have been using in India since last 20 days.
Surprisingly 5G works on Jio. Also, the phone is working as expected. GPS detection is slow though. Rest all features along with those related to mobile network are working properly. I hope this helps those who want to buy Zenfone 9/10 and use it in India.
Please check 5G bands that your model supports and the bands Jio supports.
1. Jio app will not show zenfone 9 in their list.
2. Put the sim in another 5G phone which is sold in India and open myjio app to apply for/activate the Jio 5G unlimited offer
3. Then transfer the sim back to your phone and select 5G option in the settings
Ideally it should start working as soon as the plan is activated on your device.