It depends which server-side cache we're talking about as this has usually many layers. If your application server is caching HTML to save on expensive SQL queries and template processing, then you still can use nonces by modifying the output HTML on the way back. Your templates and the cached HTML may contain placeholders like this:
This can be happily cached by the application server for days without negatively impacting the CSP nonce protection.
The nonce may be then generated dynamically on the web server using OpenResty set_secure_random_alphanum and substituted into the
REPLACE_WITH_NONCE placeholder with