I saw something on Facebook about it being brought about by a mutiny of some German armed forces. Is there any truth to that?

Yes, obviously that's a very simple way of putting it though. Historians refer to the situation as the German revolution.

The beginning of the end of World War 1 is the Hundred Days offensive between August 8 and November 11, 1918. It was a massive offensive launched by the allied forces that quickly pushed back the central power forces. By October, the casualties were massive and the Germany army was broken. The central powers were all discussing an armistice to end the war.

So, on October 24, 1918, a German naval unit decided the war was lost and disobeyed their orders to deploy. They mutineed and a day later, the naval officers got it under control and imprisoned the mutineers, but abandoned the military operation due to concerns regarding crew loyalty. The ships returned to Kiel, and once there the crewmen of the ships refused to work unless the imprisoned mutineers were free. The officers wouldn't hear of it. So the crewmen got together with the dockworkers, shipyard workers, and other labor unions which were politically connected the SPD (Social-Democrat party of Germany). Protest happens, shots are fired to control the protest, the protest gets larger, and by November 4, Kiel is in the hands of 40,000 pissed off solders and laborers. They formed a soldier's council and sent off a list of demands - their 14 point list demanded among other things, freedom of political prisoners, freedom of speech, and essentially an end to the war. From Kiel, the revolution spread and all over Germany laborers and soldiers began to strike and adopted the Kiel list of demands. By November 9th, there was a prcolomation that Germany was a republic.

Now remember, that all started on November 4, and by November 11, just a week later, Kaiser Wilhelm would abdicate and head off to exile in the Netherlands - a neutral country so that he could avoid capture. His closest military advisors all told him the soldiers weren't going to fight for him and it was over.

The newly created German government promptly signed the armistice ending the war on November 11, 1918.

The fact that a government born out of a soldier and worker revolt coupled with the socialist party lead to a convenient political myth for the Nazis. The "stab-in-the-back" myth goes that the war wasn't over yet and the army was still proudly fighting and ready to go but that the socialist/Marxist/Jewish plotters of the revolution overthrew the rightful monarch and surrendered.