I’ve been using tube amps for 25 years. I’ve never had any fireworks. I’ve lost a couple of output transformers, but that was uneventful. Depending on the circuit design, most tube amps will blow a fuse if a tube runs away. Others, it will take out a resistor, again, uneventful.
Just for a point of reference, I can count off the top of my head, 20 different tube amps I’ve owned. Never had the need to use a fire extinguisher…..