Hi @James H. Robinson ,
Welcome to Microsoft Q&A Platform.
Azure DevOps is not mandatory but is strongly recommended as it allows to automate deployments. Branching in Azure DevOps helps in better management and control of pushing all the changes to the final branch. Its not mandatory to create a new branch, Usually branching policy is followed to review changes (Once Dev branch is completely tested and approved, changes can be merged to Test Branch and to subsequent branches later). This also helps in isolating UAT code, Development Code and Production Code in separate branches. This documentation covers Azure Analysis services model creation and deployment for beginners.
You can ask the experts in the dedicated Azure DevOps forum over here:
https://developercommunity.visualstudio.com/spaces/21/index.html