Balena Etcher is an app oriented to flash OS images to SD cards & USB drives.
It has nosense having this app as the default one to open html files. In fact, and even though Firefox is my default app to open html files, Publii tries to open a page preview with Balena Etcher.
If I remove from my system Balena Etcher Publii works fine rendering a page preview properly (opening the web browser).
So, the question is: which app is working badly? Publii or Balena Etcher. As a simple user, I don’t have a simple way to find it out.
My kindly request to Publii developers is: could you, please, try to reproduce this Publii behaviour with Balena Etcher installed?
My setup: Ubuntu 20.04 x64 + Gnome under Xorg + Publii 0.38.3 (from deb file) + Balena Etcher 1.5.117 (from deb file).
I think your best bet is to make a blank.html file, right click and check it’s properties/open with and make sure the default is set to a web browser. This is probably not a Publii nor a Balena Etcher problem, but an issue with your OS config.
It may however be nice to specify which application to use inside of Publii in general. But that should probably be a separate feature request if it’s not already.