Making low-pressure-reassure lamps relies on the fact that the discharge medium is liquid or gas at room temperature. If this condition isn’t met, then you have to jump through hoops (like low pressure sodium) to insulate the discharge tube and reflect IR light. Since mercury is the only metallic element that is liquid at room temperature, it is typically the only metal present in “traditional” style low pressure lamps (excluding amalgams). But, the alloy named Galinstan (68.5% Ga, 21.5% In, and 10% Sn according to google AI overview) is liquid all the way down to -19°C/-2.2°F. I wonder if this alloy could be used in fluorescent tubes as an alternative for mercury. Obviously, you would need to completely redesign the phosphor to better suit the emission of this alloy, but I don’t think that would be out of reach.

What do you think?

You'd end up with different elements vaporizing at different temperatures. Since gallium does seem to have UVC emission when excited in theory it could work. But the boiling point of gallium at atmospheric pressure is 2400 degrees C so i think it would be a very hot running lamp, even if you were to run it well below atmospheric pressure.

I can't find a graph about the boiling point VS pressure to see if it would at all be possible to run it as a fluorescent HID lamp, or whether it could be a low temperature low pressure arc like common fluorescent lamps.

Oof, I thought that would maybe be a problem. Since the boiling point of mercury is around 357°C (much much lower than Ga's 2400°C), I think this alloy would be limited to high pressure lamps. Maybe it could be made into one of those old medium pressure lamps, but we don't use those anymore.

In fact what matters for a low pressure lamp is not the fill being liquid, but to have sufficient vapor pressure, so low enough boiling point.
In many fluorescents the mercury dose is not liquid at all (because held in a solid amalgam speck), but it still turns into gas (sublimate) quite readily, even from the amalgam (although the Hg pressure from an amalgam is lower than from pure liquid Hg, it needs few 10's degC extra to reach the same, so quite high pressures).