You don’t need my opinion or permission.
What RedHat did (trying to sell licenses for software that their customers are legally allowed to redistribute freely because it includes GPL code) won’t work, because some of their customers used their rights and redistributed the thing for free.
Selling hardware will work, but it depends what you do exactly. For example you can read about Saleae logic analyzer. They built hardware that costs only a few dozen euros to manufacture, but they sold it for a much higher price (several hundred euros) because they shipped software to use it as well. People soon found that they could use their software with much cheaper clones of the hardware, so that didn’t go well either.
If you plan to do a for-profit business, just take some time to think about where your value is, and how you can invoice your customers for it. If you try to sell a thing which is not the one where you bring value, and the thing you try to sell is available cheaper or free elsewhere, you have to consider it. The exact solution is different in each case.
So, if we imagine someone selling preinstalled machines with Linux. What will their value be? One part will be selecting the hardware, like any other hardware distributor. Another part will be making sure the machine runs well in Linux (or whichever software they package with it). Maybe there can also be a warranty (replacing the hardware if it breaks), or a support offer (having a hotline to help buyers figure out Linux issues).
If the company is just installing Linux without testing that it actually works, on hardware designed by someone else, and trying to make a profit from it? Soon enough people will find out that you can buy the same hardware from the manufacturer directly, and install Linux on it yourself. And the company can complain that they invested a lot of time in making sure Linux works on that system, and they should be paid for this, but people will not care once the work is done. They will get the cheaper machine, get the Linux patches, and install Linux themselves.
So, what can you do? Maybe you can sell the things that’s valuable (the work in porting Linux to a new hardware) separately. For example, make a crowdfunding campaign to fund that effort. Or just be a company that does Linux porting and support for other people, and don’t make or sell any hardware yourself (some of my paid job is like this). Or do your business plan so that you get money from your warranty and support offers for fixing people’s laptop, rather than from the hardware and software sales. Or, you could also design your own hardware and make it so it is not easy to clone by other manufacturers who will cut the price down.
Or, you can accept the risks of just trying to sell the thing anyways. Just be aware of it when problems will happen.
And likewise when you buy something, you can ask these questions as well. What I am paying for? What am I not paying for? Why is such product so much cheaper or more expansive than another? How much am I ready to pay?