Can't create bootable usb key with windows 10

Startup disk creator won't open the file. I click on "other", find the file, click on "open" (or double click the file), nothing happens.

Rufus - well, the "balena-etcher" equivalent - can't be securely installed.

sudo tee /etc/apt/sources.list.d/balena-etcher.list

sudo apt-key adv --keyserver hkps://keyserver.ubuntu.com:443 --recv-keys 379CE192D401AB61
Executing: /tmp/apt-key-gpghome.2JnR7EAw3P/gpg.1.sh --keyserver hkps://keyserver.ubuntu.com:443 --recv-keys 379CE192D401AB61
gpg: keyserver receive failed: No such file or directory

sudo apt update

Reading package lists... Done     
W: GPG error: https://dl.bintray.com/etcher/debian stable Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 379CE192D401AB61
E: The repository 'https://deb.etcher.io stable Release' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.

And unetbootin can't be found.

This is not the only issue. Microsoft has stopped putting sha256sum online, so I don't know whether my iso is OK.