I am unable to install mongodb-org 4.2 for ubuntu Focal. It appears the server repo is missing
No, it is not supported on this platform.
MongoDB 4.2 Community Edition supports the following 64-bit Ubuntu LTS (long-term support) releases on x86_64 architecture:
18.04 LTS (“Bionic”)
16.04 LTS (“Xenial”)
MongoDB only supports the 64-bit versions of these platforms.
MongoDB 4.2 Community Edition on Ubuntu also supports the ARM64 and s390x architectures on select platforms.
Welcome to the MongoDB community @Justin_B!
As @chris noted, Ubuntu Focal (20.04) isn’t a supported platform for official MongoDB 4.2 packages.
Ubuntu Long Term Support (LTS) releases like Focal are generally supported starting from the next major MongoDB server release following the LTS release, which in this case would be MongoDB 4.4 (July 2020).
I’d recommend installing MongoDB 4.4, instead. For information on what has changed, please see the Release Notes for MongoDB 4.4.