The last couple of days I've been fiddling with Ventoy alternatives. Asking around, I was reminded of hardware devices that do a similar job, but are much more reliable. Researching about them, I see people using Linux USB "gadget" mode to do this.

Just tried, worked in a few minutes. Magical!

(The time I've wasted looking for more esoterical alternatives.)

TL;DR: you can use a Raspberry Pi (or whatever) to present a file with an ISO as a USB disk. Works like a charm.