Install Ventoy on a USB flash drive. Copy the ISO - copy as in cp. That's it.
You can add as many ISOs and select which one to boot with.
7bit
Ubuntu's Install medium supports secureboot. (As do many other Linux install mediums) I assume ventoy requires SB to be OFF, which does complicate things more, than just using Rufus.
Install Ventoy on a USB flash drive. Copy the ISO - copy as in cp. That's it.
You can add as many ISOs and select which one to boot with.