I did an update (upgrade?) from 42.1 to 42.2 the other day. It seemed to go pretty well considering the amount of “stuff” on my system. I did have to hunt down the System Settings program and add it to the menu. However, as my title shows, my default browser seems to now be Chrome, rather than Firefox and, try as I might, I just can’t seem to change it back. System settings shows Firefox as the default, Firefox shows itself as default, Chrome says it is not the default, yet when I click on a link it opens in Chrome. Is there some secret place where there is a setting I am missing? I really hate to use the MS method of uninstalling and reinstalling!
You using Firefox and or Chrome points to the fact that you most probably use a Desktop Environment. But it is unknown to us which one when you do not tell.
You could try launching firefox clicking file- preferences and setting always check that firefox is your default browser. That might take care of it what ever desktop you are using.
However if KDE startbutton- settings- system settings- applications. Default browser and others can be set there along with file associations etc.
check the mime settings for html files. My bet is that Chrome is on top
Systemsettings - Applications - File associations. Search for html and change the order preference.