Low Beams dead, Hi Beam Fine?

my 2 cents and likely already covered by others in here. With the car in the no low condition

Everything plugged in. Probe the output wire from dimmer switch for low beam, some are violet in color. Hot? Yes.
Do the same thing at the engine side of bulkhead where that wire passes through. Hot? Check from the compartment side too.
Probe the oem headlight plug, hot.
Pull relay from block or plug and probe the trigger terminal for heat. Check that the trigger/ground terminals are not pushed out of the block/connector.

Four simple test light things to do that will narrow down where the issue lies.

Check feed into relay power side 30 terminal as well. Is it fused? (Don't think it is this as it is intermittent)

You know it isn't the switch because the high beam works and is fed with the same wire into the dimmer.

Could be dimmer, crappy/intermittent bulkhead connection, bad engine compartment wiring.