Is it possible to embed Community page inside normal Salesforce page? I tried using iframes but they don't work because of Content Security Policy. The only workaround I found is to redirect the internal user to Community using a link, but I'd rather have it embedded inside standard UI. Thanks for the help.
You are trying to embed the components available in Community Builder within Internal Salesforce Org's pages -- that's not possible. Components available in Community Builder are specific to what can be used in context of Communities.
Only if you have a custom lightning aura/web component or a custom visual force page, then only you can utilize it both within Internal Org and Community.
The standard way for letting Internal Users to access Community pages is by adding them as member of the Community and let them access Community.