I used to type umlauts and other keys (ä,ü,ö.æ,å,ø, etc) directly from the keybord into emacs, and latex never complained about these letter, as long as I used \usepackage{isolatin1}.
Today, I discovered that this does not work anymore, neither on my laptop, nor on my workstation.
I absolutely have no clue where to look for the parameter that might have changed. Perhaps someone has an idea?
(if that resolves it, I think you put this in .bashrc, maybe someone else can confirm, or they’ll spell it out in one of those links)
Otherwise, I had luck finding if there were any problems with my locale settings–you’ll receive errors if there are faulty settings-- with the following command: