Hello and welcome!
As you discovered, with a single job you cannot target two locations. What you did (two jobs) is one way to accomplish this, and it’s how I did it when I first started using Duplicati. I didn’t like that Duplicati had to do the work twice, and I didn’t like that the two backups weren’t identical (they run at different times - the web UI engine cannot run jobs simultaneously). It was also annoying to have to manage 2x as many job configurations.
Because of those issues I switched to having Duplicati only back up locally (to my NAS), and then I sync the resulting backup data to a remote destination with a third party tool. rclone is excellent for this, but I actually use the “Cloud Sync” program on my Synology NAS to do it.