Asking people for money is the best way to validate a business. If people pay enough for a profit, the idea is valid. If they don't it isn't.
You can ask people to pay before there is a product. Asking people if they will pay is not the same thing because it is less bruising to the ego.
Competitors don't matter so long as people are paying enough for profits...just don't take out a big loan and do talk to your customers.
Good luck.
There are companies doing something similar such as Coolify and elestio.
You’re thinking in technical terms, but you need to focus on what’s the value for the user. A nice framework I learned the hard way is: so what? Always ask yourself this question until there is nothing to ask.
Once you find the value, then just search for it and you’ll find your competitors. In your case for example, managed wordpress hosting.
Edit: typo
I'm working on a product that may allow you to find competitors' customers through a search engine for the web's HTML. If your competitors happen to put specific HTML in their customers' websites (some HTML tag, a JS library, etc), you could get a list of prospects, which could help validating your idea for specific products.
Here's an example for Discourse: https://www.datafragment.com/search?q=discourse-cdn.com&page... It is freemium: creating an account gets you some free searches with full search results.
Happy to chat more if you're interested. We're focused on the French market currently but could expand depending on demand.