How do PSMH dimmable ballasts behave. I plan to retrofit a fixture for my home office. I assume I can just use a dimmer labeled for LEDs, but it it's one where you click it on and then turn it to brighten it, what would happen if I just turned it barely on. Would it not work? Repeatedly try to start? Would it actually light dimly. I'm aware of the Lutron Controls where there's separate switches to turn on / off and set the dim level but Lutron stuff is expensive.

I would expect that the ballasts use control signal on a separate port (1 to 10V, DALI, ..) and are not dimmed through the power input

That is correct, the ones I'm looking at are a knob, clicking it to the right closes the mains contacts wire. Continuing to move it raises the control voltage wire from zero through 10 volts. What happens if the lamp is off and I just click it without rotating the dial, supplying power to the mains and 1 volt to the dimming input?

Digital dimmable ballasts usually waits 15 mins at 100% power to let the lamp warm-up, than operates the dimming.