If the problem is, is the thing I downloaded the thing I'm going to boot and the issue is you don't trust the thing you downloaded the software on, then the only way to solve is to use a separate device.

Like on a different laptop read the sd card and verify it.

But this is kinda moot anyway. Just download the image onto a reasonable machine. I.e. boot tails, download seedsigner, verify on tails, and then flash.

I would say a CD is cooler than a microsd. Nobody shows off their microsd collection.

I might be a little skeptical of how the write once is done in the firmware of microsd controller, but ultimately yes, they are equivalent.