I can't find KeyStone among the plugins either, but KeyStone Bitcoin Only Firmware is compatible with Electrum.
I found the documentation of their DIY wallet (
the link in DaveF's reply is for their desktop wallet)
Link to Specter Shield DIY doc:
https://docs.specter.solutions/diy/And based from the "
communication" options (
link), it cannot support transaction export via QR since Electrum shows base43-encoded data instead of base64 in its QR code.
On the other hand, SD card should be supported since Electrum exports in PSBT format; however, signed transactions should be in hex for "
broadcast" button to be available.
There's only one way to find out: try to 'export->sign->import' a transaction but don't broadcast if you don't want t send it.