I have an F20T12 trigger start ballast that currently runs a lamp with a broken cathode. When I insert only one pin on the end with the broken cathode, it starts to flash orange, blue, and swirl while the whole tube flickers madly. My parents would get mad if it lost vacuum. The ballast has a 215 volt OCV.

iwhen you loose vacumme lamp sucking air In and  mercury tend stays in the tube.being a 2 lamp  trigger start  it needs high OCV to run 2 lamp in series. many times lamp will runon one bin in rapid startt.  but you will get very shortlife if one end is heated and ither end not  making contact both pins.  the non heated end will sputter off .  that why your seeing all kinds of flashes
and sputtering.   rapid stsrt and trigger start seldom
looses vacumme though.  when cathode breaks
it usually be dimmed or wont start at all next  time
you throw a switch.

Normally with rapid start and even trigger start, the lamp will simply have trouble firing up. The more you start it up,
the longer start up time will be at this point. It *might* not lose vacuum, but it's not impossible. I've actually had an F15T8 lamp loose
vacuum not too long ago. That was on one of my: 1 lamp GE Bonusline 0.32amp 0 degree Trigger Start ballast(s). I've had another
F15T8 lamp lose vacuum as well on a regular 1 lamp GE Bonusline Trigger Start ballast, (0.28amp) but that was because the electrode
filament melted apart and fell on the glass, resulting in a hole through the glass. That EOL show, even with that ballast,
was also still very entertaining. Brilliant orange flashing, brilliant orange swirling... etc.

iwhen you loose vacumme lamp sucking air In and  mercury tend stays in the tube.being a 2 lamp  trigger start  it needs high OCV to run 2 lamp in series. many times lamp will runon one bin in rapid startt.  but you will get very shortlife if one end is heated and ither end not  making contact both pins.  the non heated end will sputter off .  that why your seeing all kinds of flashes
and sputtering.   rapid stsrt and trigger start seldom
looses vacumme though.  when cathode breaks
it usually be dimmed or wont start at all next  time
you throw a switch.

It already had a broken cathode. It looks like an EOL on an HF instant start ballast. The ballast is a 1 lamp LPF ballast.

 ... OHHH... oops! Forget everything I stated before in my previous comment. I was thinking your ballast was a 1, or 2 lamp
HPF Trigger Start ballast. Since it's a 1 lamp LPF Trigger Start ballast, the way it'll behave with an EOL lamp, should be totally different
from how a HPF Trigger Start ballast behaves. I'm pretty sure you should get a violent EOL show, and also rectification... similiar
to what you'd see on an Instant Start magnetic Slimline ballast, on the blue wire side. At least I think that should be the result.
I could be wrong... but regardless, I'm pretty sure it'll be tough on that 1 lamp LPF Trigger Start ballast. Don't those ballasts over heat
with EOL lamps?

... OHHH... oops! Forget everything I stated before in my previous comment. I was thinking your ballast was a 1, or 2 lamp
HPF Trigger Start ballast. Since it's a 1 lamp LPF Trigger Start ballast, the way it'll behave with an EOL lamp, should be totally different
from how a HPF Trigger Start ballast behaves. I'm pretty sure you should get a violent EOL show, and also rectification... similiar
to what you'd see on an Instant Start magnetic Slimline ballast, on the blue wire side. At least I think that should be the result.
I could be wrong... but regardless, I'm pretty sure it'll be tough on that 1 lamp LPF Trigger Start ballast. Don't those ballasts over heat
with EOL lamps?

The ballast already runs very hot with a good lamp.

It might heat up to the point of tar spillage then with an EOL lamp. That would suck