On Wed, 7 Feb 2018, Michael Berger wrote:
Rich, this is indeed annoying and one must wonder why this reappears again and again although one does not at all use such "outdated font commands".
Michael, As far as I can recall, this is the first time (perhaps the second time) I've encountered this issue in the many years I've used lyx.
Fortunately, there is an easy cure.: In > Document > Class > Custom add this: enabledeprecatedfontcommands
Thanks. That does the job.
You find this cure if you scroll further down in the Description Window of your Error Message.
I certainly missed that, Best regards, Rich