The electrum install to USB is messy and instructions are inaccurate. Running the electrum-4.5.5-x86_64.AppImage on the host computer doesn't install to the USB.
To clarify things, is this the documentation that you're referring to:
https://electrum.readthedocs.io/en/latest/tails.html#?because there's not other "
DIY USB" article in Electrum's official documentation.
If so, the Appimage isn't supposed to be installed, it should be set to be executable written in step 7.
A prompt window says Electrum wallet -> Wallet: default_wallet -> Choose... -> choose the USB path /media/hostComputerUsername/USB -> File name: there are no files, so the Open button is faded out?
That specific "
Open" button will only work if you have clicked to a wallet file using that file (
wallet) selection prompt.
Usually it opens the directory of the last loaded wallet so if your wallet is in another directory, you should browse to its location.
You should check if it in your "
persistent storage" (
have you enabled it as pointed in step2?) or else, it'll be deleted in every restart.