I cloned the repo from GitHub, uploaded it to my server to an analytics folder at my site’s root, then attempted the install via https://mysite.com/analytics/.
This gave me a few errors related to Composer and meant I had to run:
The error you are seeing is therefore also not from Matomo, but from composer. It tries to install guzzle/guzzle which needs the curl php module. But the PHP you used to run composer with doesn’t have curl installed. (Maybe it is a different one than the web version)