Okay, so when you say “filament” it’s more a form-factor (similar to COB LEDs but on a string vs on a board), and not a heated filament as in incandescent bulbs.
I was curious what kind of phosphor would be thermally excited to produce light… that’s what threw me by use of the term “filament”.
So it would in fact be subject to flicker, etc., if the driver passed through voltage variations (hiccoughs) in the mains supply.