Could I use an Electrum installed android phone to sign transactions generated by sparrow watch-only wallet?
If so, it may save me much time and efforts as I don't need to install linux deploy things on my old cellphones.
That's quite the setup.
But the answer is yes, both Electrum and Sparrow use "
Partially Signed Bitcoin Transaction" (
PSBT) export but Electrum is specific on its supported format.
Here's how to export an Electrum-compatible format:
After creating the unsigned transaction in sparrow; "
Click File->Save PSBT->To Clipboard->As Base64"
Then transfer that copied text file to your phone through your preferred method.
To Import to mobile Electrum, copy the base64 PSBT string, use "
Send" then "
Paste from clipboard".
You can also use: "
Click File->Save PSBT->As Base64" to save it as a text file that you can transfer to your phone.
Open that txt file and copy the contents then do the last step above.