There is no guarantee that even with dimmable bulbs it will not flash or flicker, the old EU rules say if not dimmable it must say so on the bulb, but it does not say with what it can be dimmed with, so you have all sorts of dimming methods, first I used was series/parallel switching used with old cine lights, also seen rods which are dropped in liquid, but in the house we have 2 x 2 types of dimmer, first pair is leading or lagging, second pair with or without a neutral, and then as well is the size, some only go down to around 20 watt and some will only go up to 100 watt, there are 5 watt to 400 watt versions, but just having a dimmable bulb and a dimmer does not mean it will work.
In the main a dimmer switch or for that matter any electronic switch which does not use a neutral has a lower limit of 5 watt, and it seems to be bulb size rather than cumulative bulb sizes. So 5 x 2.4 watt G9 bulbs did not work, but one 5 watt G9 bulb did, the problem is the resistors used to allow a small current to work the switch without lighting the light produce heat, so the very small bulbs don't have them built in.
Toroidal transformers and wire wound ballast have an in-rush current, which most dimmer switches can't handle. This does not mean they can't be dimmed, it just makes it harder, I have a variable transformer with an output zero to 250 volt and I am sure if I mounted it in a box with cooling fan it would dim nearly any bulb which does not require a strike voltage or has built in regulation. But it was expensive and would not fit in a standard switch back box, but if this will dim a bulb, then the bulb is dimmable, even if not dimmable with a normal dimming switch.
