Why not provision a new server with 20.04 and move the data over ? I assume the project is in git, so its just the database and storage files that needs to be moved.
@Sinnbeck I agree with @sinnbeck - it's what I did. Provision a new server with the tech you require, pull down the project, moved the DB and potentially storage if it's not in an S3 bucket. You can potentially wire up a different domain to it, or subdomain to it first as an alias to make sure everything works as you expect before you migrate the proper domain over.