what is best free vanila host site?
This is such an open question, and these sort of post attract spam, so I'm reluctant to encourage it.
Often the best free webhost are not the traditional web hosting solution, but some cloud based code platform service. They are free in the sense that on minimum specs they don't cost, however you may need to crank them up pretty quick. It does require more technical skills than the average person.
Free host are rarely that good. It is hard enough to find a good cheap one. They nearly all have shockingly poor practices.
I suggest you search for general host that meet the requirement becuase you really don't need a "vanilla host", and do you own research. All you are goign to do here is get responses are the odd post about free host you will be none the wiser.
There is a lot of competition in web hosting, so the the best free host for vanilla are the best free hosts in general. You just need to make sure the minimum specs are met. I might also mean to some addon you cannot use. The cheaper the web host the less control you have, over what is possible.
if a host advertises as vanilla host, this alone should not be a deciding factor. All that means they have a one click installer. You should avoid one click installer, they usually install outdated versions, and sometimes bad forks.
grep is your friend.