No they do not have to be from the same manufacturer. None of my appliances in my kitchen are from the same manufacturer. Bluestar range, Electrolux warming drawer, Bosch dishwasher, LG fridge. They are all stainless steel though so they match in that respect.

Appliances should be chosen for performance. Buy the best appliance you can afford. Just buy the same color (or the color you eventually want them all to be.)

We went with white from 4 different manufacturers. We found white was a consistent color across all brands.

After reading reviews, talking with sales people and repair folks, we view appliances as shorter term compared to cabinets and countertop. Thus, we did not buy the best we could afford but bought what does the job.

Thanks for the responses. This is NOT for my home. It’s for a flip. If it were my own, I’d do what I wanted... with all the kitchen pics I’ve seen of builds and remodels, they all used the same vendor with the exception of refrigerator...

If it's for a flip, then that changes things a bit. It's a business decision rather than personal. By going with the same brand, you'll probably get discounted package pricing, and they will look very consistent for a buyer, like in a new construction home. Depending on what buyers expect in your area, you can advertise it when selling (i.e. "with all new KitchenAid appliance suite" helps brand the experience for a buyer).

I certainly wouldn't say it's a must for them to all be the same brand, but they should all be stainless steel to match. Personal opinion, I'd like the handle styles to be consistent. I really dislike one appliance having a curved handle while another has pro and another has rectilinear. Given appliance constraints right now, you may be forced to have a blend based on what you can actually get your hands on. Definitely don't want to hold up selling your flip because you're waiting on appliance orders.