Can I link a joint bank account to my ATS account?

Yes, you can link a joint bank account to your ATS account in which you are one of the holders. The process of linking the joint bank account is same as adding a secondary bank account. See, How to add a secondary bank account to my ATS account?

Note: If you are adding funds through a joint account linked with multiple ATS accounts. It is advisable to transfer funds through UPI/BHIM.