Sidecar not available
How can I use my iPad as a second display for a Macbook Pro (2015) that is not compatible with Sidecar?
MacBook Pro 13″, macOS 10.15
Question marked as
You can’t… Because it isn’t compatible. There are no known workarounds (and obviously the workarounds aren’t officially supported).
You can try something like Luna Display or Duet Display (both third party software, that requires purchases of some manner).