5th dnd – Increasing the damage done by the breath of a dragonborn would help to balance them?

Dragonborn is one of the weaker races in the game, as confirmed by the answers to my other recent question: How could the addition of a dark-eyed racial trait to Dragonborn's balance affect it?

It seems to me that part of their weakness, at least, is that their breathing weapon is underpowered, so in another attempt by mine to bring them into line with the other playable races, I'm considering how to increase the Damage can help balance them, and how much to increase it.

As before, my goal is to make them more attractive to players, but not make them too strong to master them. Ideally, they should not be better than a mountain dwarf (one of the strongest but always balanced playable races) at most.

So, in this spirit, here is the damage caused by their breathing weapon, RAW:

A creature takes 2d6 points of damage in case of failure in a save and half the damage if successful. The damage increases to 3d6 at the 6th level, 4d6 at the 11th level and 5d6 at the 16th.

I have considered the following:

  • Damage increase of 1d6 in total: this would give 3d6, which will increase to 4d6, 5d6 and 6d6 as their level increases. My concern is that 3d6 would be very powerful for a level 1 character, but 4d6 is not very impressive for a level 9 or 10 character …
  • Damage increase from 1d6 to level 3 only: this means that the damage remains at 2d6 at level 1, but is increased to a more respectable level 3 at level 3, and the progression after is very similar to the option above, but still at higher levels. I wonder if it's still a little skinny …
  • Increases damage by 1d6 more often: by adding increases to levels 3, 8-9 and 13-14 (you have not decided yet exactly), so that a level 1 character always has 2d6 but at level 3 it's 3d6, which is a bit more respectable for a level 3 character, and at level 6, it's 5d6, according to my previous option. However, it starts to increase more quickly and we end up at 8d6 at level 16, which is comparable to a fireball or lightning fate, but on the other hand, a level 5 demon demon can cast two or three fireballs by short rest, is it so bad for a level 16 dragonborn?

As you can see by my rationalizations about Fiend Warlocks, I'm tempted by the last option, but I'm afraid its speed makes this feature too powerful. Even races that have an innate spellcast (ie a tiefling, a newt, etc.) do not have an offensive third-level spell, so maybe the second option is the better one?

Since it is difficult to evaluate using the tools mentioned in the answers to my last question, I hope there is a better way to judge the power of such increases to make the original dragon breed more powerful than it is, but no more powerful than a mountain dwarf at maximum in terms of balance. Which of my options above would achieve the type of balance sought?