Hello,
... of template to /var/lib/dokuwiki/lib/tpl ...
It seems you are using debian/ubuntu prepackaged DokuWiki. Template version must match Doku versions. Debian/Ubuntu doku packages are known to be old. check
https://www.dokuwiki.org/template:arctic#previous_versions
Because in the present template I can not find Extension manager for templates
That's a matter of version, not template. Template manager is available from binky on, I think, or maybe ponder stibbons.
/Schplurtz