I initially tried this with Ubuntu Linux and a .tar.gz file without the composer tool. I was using MySQL and PHP 7.4. My problem is about the same with my second attempt. I will now describe my second attempt and ask for help with it (instead of my first attempt).
I am trying to install CraftCMS on Debian 10 with composer. Everything seems to work on the back-end. I am using PostgreSQL and PHP 7.3.
I finally went to the web front-end portion of the directions. In a web browser I go to /index.php?p=admin/install
It resolves to /dashboard. The web page that is rendered says "Not Found The Requested URL was not found on this server"
When I just go to "" in the web browser, I see "Welcome Thanks for installing Craft CMS!" I can click on the "Control Panel", but that takes me to a page that is Not Found.
I expect to see the screen to install CraftCMS in a web browser when I go to /index.php?p=admin/install
What am I doing wrong?