If you’re playing a character using the options presented in the Unearthed Arcana articles (or if you just like to see the design process at work), you may want to know exactly what changed between the UA article and the final release in Fizban’s Treasury of Dragons.
The damage progression was changed from “the same as the PHB Dragonborn but with d8’s” to a new d20-based progression that starts lower than the PHB Dragonborn, but finishes higher. Every new dragonborn variant’s 3rd-level trait (Chromatic Warding, Metallic Breath Weapon, Gem Flight) was delayed to 5th level.
The Chromatic Dragonborn’s Chromatic Warding was shortened from 10 minutes to one minute, and was delayed to 5th level.
The new version of the Kobold didn’t make it to print. But don’t lose hope: it will almost certainly be updated in Mordenkainen’s Monsters of the Multiverse.
Way of the Ascendant Dragon
The Ki cost to use Breath of the Dragon beyond the proficiency-based number of uses was increased from 1 to 2.
Wings Unfurled was reworked significantly. You no longer get a few free uses. Instead, you can activate it when you use Step of the Wind, but you can still only use it a numbers of times per day equal to your Proficiency Bonus.
Aspect of the Wyrm was rewritten. The “waves of destructive energy” option was replaced by Frightful Presence, you now choose one effect rather than getting both (so either Frightful Presence or damage resistance), and the cost to activate it again after the free usage per long rest was reduced from 4 ki to 3.
Ascendant Aspect’s blindsight was reduced from 30 feet to 10 feet, and the initial damage was reduced from 4d10 to 3d10. The ongoing damage effect added to the breath weapon was removed (it looked like a nightmare to track) and replaced with the ability to empower your breath weapon by spending an additional Ki point to add another damage die and double the range.
The Drake Companion no longer has a time limit. It remains until reduced to 0 hit points or you summon another one. This means that you can keep your drake around permanently. You can only summon it once per day for free and again for the cost of one spell slot, so you can feed it to monsters repeatedly at almost no cost.
Bond of Fang and Scale no longer allows you to choose between a flying drake or an amphibious drake, but now you can ride your drake as a mount.
Drake’s Breath damage increased by 2d6.
Perfected bond now allows you to ride your drake while it flies, and Reflexive Resistance was given a usage cap equal to your Proficiency Bonus per long rest, so you can no longer us it every round forever.
Gift of the Metallic Dragon’s AC bonus as changed from a d4 to a flat number equal to your Proficiency Bonus.
Flame Stride was renamed to Ashardalon’s Stride.
Draconic Transformation’s fly speed was increased from 40 feet to 60 feet, and the breath weapons range and damage we both doubled (30-foot cone to 60-foot, 3d8 damage to 6d8).
Icingdeath’s Frost was renamed to Rime’s Binding Ice, and the size of the cone was doubled.
Raulothim’s Psychic Lance got some important updates. The most obvious is that the damage was reduced from 10d6 to 7d6 and that targets now take half damage on a failed save rather than taking none. More important, the phrase “and the spell slot is not expended” was removed, so you can no longer use this to walk around and hunt for creatures using their name. You could still use this to murder some poor sot from 120 feet away through several walls, but you generally need to know where they are before you start burning spell slots.