Is the MTB a 26" wheel? The road bike will likely be a 700c wheel, so different sizes and not swappable.
Even if they were the same rolling size of wheel, then brakes are a sticking point. Either both need to be rim brakes or both disk brakes. A road bike with disk brakes would still be fairly new and worth more as-is, not chopped around.
You'd have to take the whole front fork from the MTB to the road bike to get the disk mounts, at which point you've made a lightweight frame front-suspension MTB.
Brake cable pull will be an issue too - your brifters will pull less wire than the MTB brakes. So rim brakes will move less when pulled by brifters. This means poorer braking and more brake rub because of smaller tolerances. Any fixers tend to be patch solutions that don't address the underlying causes.
The general consensus is that a drop bar swap is not worth doing UNLESS you have all the parts, and don't mind losing a working bike.
Alternative Consider selling on both of your working bikes, and buy the new-or-used bike you want to own.