this is real helpful but how i can install electrum in my airgapped device ? plug USB flash memory to the device to install the electrum ? if so thats not really an airgapped device anymore, im really newbie in cold storage thing sorry if i don't get it yet
You can use a microSD card with an adapter. Plug the microSD card using the adapter into your online computer, transfer the file on the microSD card and slide the adapter's lock/unlock switch down as you can see in the below image to make it read-only so the file can not be modified. Then you can connect it to your airgapped computer.https://kb.sandisk.com/app/answers/detail/a_id/1102/~/sd%2Fsdhc%2Fsdxc-memory-card-is-write-protected-or-locked
You can use CD. Copy the file to a CD from your online device and load the CD on your airgapped device.
Or you can use a USB flash drive that has a read-only switch as well.
Download Electrum from https://electrum.org and verify it signature for authenticity