I get already Matomo installed on GCP like official click to deploy and it worked well. Now I switched to Plesk and no chance to get it to work by following tutorial from docs (100% - firewall disabled and PageSpeed disabled). P.S. - Plesk is running on Litespeed Fast CGI.
Finally I started fresh instance of GCP (again) and I get 100% same situation. So, NOTHING TOUCHED (click to deploy), mean - running Matomo from IP, by adding first site, site is not recognized. So, here is nothing from above specific moments (firewall, LS,...).
After adding tracking code of first site to WP site, by login on Matomo, I should to see dashboard with initial site tracking widgets, but I still see warning page that tracking code is not added.
I suspect that issue is OS - Ubuntu 20.04 (Plesk) or Debian (GCP click and deploy), as it looks how Matomo runs on CentOS 8 (CyberPanel).
I tried to mess with permissions on Plesk, but no results. However, that cannot be the case on GCP click and deploy.
On GCP is no steps. Install it, run it and see the issue.