Renaming columns and adding columns

Hi ebjim 
Thanks for using Fabric Community.
Yes you are right. Currently rename a table in lakehouse, and ALTER table functions, adding new columns in a Lakehouse table is not supported in Fabric.
sp_rename is supported for Tables, Stored Procedures , Views and Functions in Warehouse. It is supported only for objects not for columns.

Hope this helps. Please let me know if you have any further questions.

You can change the schema of a lakehouse table by using a notebook and advancing the schema if your table is a delta table. The lakehouse sql endpoint won't let you do any schema (or data) modifications.