@AzureUser2023 Thank you for reaching out to Microsoft Q&A, Yes ISE is going to expire in August31 2024 since underlying ISE is dependent on Cloud service is going to be retire as well as mentioned here.
Refer to blog post to know more about the ISE retirement.
If you want to limit the outbound Ip address to single Ip then you need to create a standard logic apps with virtual network integration enabled and followed by NAT gateway.
Standard logic app uses app service plan as underlying it will provide a list of outbound Ip addresses.
Feel free to reach back to me if you have any further questions.