An alternative option is Ubuntu iso on usb using Ventoy with persistence . The difference was you only got a 1gig dat file to store persistence changes but i think recent release you can now increase past 1gig - how much i'm not sure
The above procedure assumes you have (downloaded) desired Ubuntu ISO file and used "Startup disk creator" to "transfer" ISO to your USB drive. Then you can boot from such created USB bootable drive and follow the described procedure.
Apparetly "Startup disk creator" only creates FROM Ubuntu ISO files, not as asdvertized from ANY ISO files.
Secondly - using large > 1TB or multiple drives slows down the Ubuntu installation procedure to the crawl.
Install Ubuntu on multi-boot / multi drives system and NOT using defaults can be a challenge.