If you want to run the appimage you will need to first make it executable.
chmod +x etcher.appimage
Secondly, the launcher fails with this error.
[16072:0715/123308.833525:FATAL:setuid_sandbox_host.cc(158)] The SUID sandbox helper binary was found, but is not configured correctly. Rather than run without sandboxing I’m aborting now. You need to make sure that /tmp/.mount_etcherF4zgMU/chrome-sandbox is owned by root and has mode 4755.
/tmp/.mount_etcherF4zgMU/balena-etcher-electron: line 10: 16072 Trace/breakpoint trap “{script_dir}"/balena-etcher-electron.bin "@”
I ran the appimage with sudo and it launched fine for me.
I renamed the file etcher.AppImage, so this would be my terminal command from the directory with the AppImage in it.
sudo ./etcher.AppImage