Have you tried using Ventoy? I've had so many issues trying to get the iso into a bootable usb either through etcher or rufus, and my experience was always hit or miss. Ventoy, on the other hand, just works.
It's pretty simple! Flash the Ventoy image onto your USB, it will create 2 partitions on your USB, one to boot the Ventoy bootloader, and then the rest of the storage space is left free to put the iso files on it (fat32 partition).
When you then boot your machine off the Ventoy USB stick, you'll get a screen with a listing of all the ISOs you saved on the USB stick, and it will boot right off the image without having to write it to disk.
Just make sure your USB storage capacity is large enough to store the ISO file.