When the elytra is deployed and the player tilts downward at a steep enough angle, the braking feature of steampunk boots is activated, slowing the elytra dive to the braking speed. This might be intended behavior, but it makes elytra flight less fun imo.

Possible fix could include changing line 55 of SteamTechArmorEffect.java:

-            if (velocity.getY() < -0.75) {
+            if (velocity.getY() < -0.75 && !entity.isFallFlying()) {

There could be a brakeWhileFallFlying config entry to enable/disable the behavior as well. I'm not sure if it'd be ideal to still negate fall damage, or if the player should still take damage when diving into the ground too hard.

Everything nerfing the elytra is good :)
No but really, thanks for the fix, will apply it once time! Will also rethink damage mechanics in that case.