Hi @Cooling, Steve Welcome to the Microsoft Q&A platform, thanks for posting the question
Yes, it is possible to create a Linked Server from Azure Managed Instance you need to ensure that network paths are open to your on-prem server and make sure that outbound NSG rules and DNS resolution are set correctly on the MI subnet, also any firewalls are removed from on-prem server that would block traffic.
It also depends on how you set up your on-prem network, you can test DNS resolution and ping from SQL Agent to make sure that connectivity (networking) is OK, then set up a linked server.
this blog can be useful for testing connectivity
Please let me know if you find any issues.
Regards
Geetha