I am using '''Thunderbird 78.13.0''' on two machines: 1) An older desktop with Kubuntu 20.04 2) A new notebook with Kubuntu 21.04 On machine 1 there is a strange (probably buggy) font behavior. I made these selections in "preferences | language & appearance": -- "allow .. other font" checked -- "use fixed .. plain .." checked But when reading HTML messages (not plain font), either incoming or my own, the program understands them as plain text and displays them incorrectly in fixed width font. This problem does not occur on machine 2. Screenshots attached. Please advise.