I have a Magento 2 installation with Varnish and Redis. Can I install and use the Litemage cache with this combination?
If so, what should I pay attention to?
There is no special way or method. Varnish is a page cache for HTML output and Redis is a MySQL cache, so there is no need for special adjustment to work each cache, but Redis is obsolete if a page is already cached. You can use Redis indepentently if any other page cache used.