Installation on OpenSuse Leap I get following two warnings:


  Due to the settings for ServerTokens in httpd.conf, it is impossible to accurately determine the version of Apache running on this server. The reported value is Apache, to run Drupal without mod_rewrite, a minimum version of 2.2.16 is needed.


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  PHP OPcode caching can improve your site's performance considerably. It is highly recommended to have OPcache installed on your server.


It would be nice if someone could help me with some pointers about how to solve this problem.
The first error message is saying that, basing on headers returned from Apache, Drupal is not able to determine which Apache version the server is using. If you have access to the httpd.conf file, you can set ServerTokens to at least ServerTokens Min, so Drupal will be able to check which Apache version the server is using.
If you know your server is using at least Apache 2.2.16, you can go forward and proceed with the installation. What you are getting is just a warning for you to check the Apache version, since Drupal cannot find out that.

The other message is telling you that it should preferable to install the OPcache extensions, which means you need to have access to the php.ini file, and being able to install extensions on your server.
If you aren't able to do that, don't do anything. That is not an error message, but a warning message telling you it is preferable to have OPcache enabled to make Drupal faster, but Drupal 8 works also without it.