Milk

It’s up to you what type of milk you want to switch to, but yes you can just switch to something like oat or soya milk.
I think cows milk is the norm because of the amount of protein and nutrients in it but if you’re making it up elsewhere in their diet then you don’t have to overthink it.

Depending on if they’ve had it before or not (i.e. in cereal etc) they might not like a straight switch, but you can offer and see how they go.
Or you can do a mix of formula and milk and do it gradually. Adding less formula and more milk each time.

I did it gradually and also offered a small cup with their lunch.
Took about a week. And I always gave straight from the fridge so you’re not faffing around warming milk.

Depending on how much food they eat will depend on milk intake. Mine were on two bottles by 1yr (morning and night) but soon dropped the morning bottle once they were eating more at breakfast.

We did homo goat milk for my son. I'm cmpa and I drink it so it just made sense to us.
I would just switch out an oz at a time every few weeks.

When you switch make sure to do it gradually. Don’t go from full formula to full something else. It takes time for them to get used to the taste.

Also for CMPA, have you spoke to a dietitian to try the milk ladder? If not look into it. It’s good for CMPa babies to be exposed to cow milk protein over time to see if they’ve outgrown it and how severe the allergy still is if they haven’t.

Dr. Lauren Hughes is a pediatrician and mom who did a great short video on this. She said to just use whatever milk you use at home.