-50 degrees is unrealistic. Even mil-spec components won't work that cold. It sounds like you just tossed that out there, so I'll assume you mean something more practical.
Your experience with fluorescent lights has been disappointing because you're using J random cheapie fluorescent lights, with no regard to their cold performance.
What you need is a programmed start ballast. Those work a different way. You know fluorescent tubes have preheat filaments (not unlike an incandescent filament) in the ends. Those can "warm up" the tube so it takes a much lower strike voltage. That also means less spallation on startup (the thing that leads to black rings on the tubes), which greatly increase tube life. The colder the bulb is, the higher a voltage it needs to strike.
Instant-start ballasts, the stock-in-trade of cheapie fixtures, don't even bother using the preheats. They just apply a very high strike voltage. But even that is not high enough to strike an ice cold tube.
Rapid-start ballasts use the preheats, but after ~0.8 second they just slam on a high strike voltage to "force" it to start.
Programmed-start ballasts run the preheats for as long as it takes, which isn't real long with 700C filaments warming the gases in the tube! Meanwhile they apply a very low strike voltage (only enough to strike a warmed tube) which is easy on the tube.
Programmed-start ballasts are readily available for $20-ish. Since they use the filaments, they need 2-wire non-shorting tombstones, so if you currently have instant-start ballasts, you'll need to change the tombstones.
LED, if it's well-built
A competently built LED will also work just fine in the very cold, assuming the driver and LED can handle the temperature. It will come on instantly and reach full brightness quickly as the chip itself warms up. Actually, it will run slightly more efficiently in the cold.
If you really must operate at -50, preheat the fixture
Add some resistive heaters on thermostats, so they preheat the fluorescent ballast, LED driver and LEDs proper. They should shut off once the device they're heating reaches 32F. You don't need to preheat the fluorescent tubes; the programmed-start sequence will do that.