Ask HN: Single Page App Feature Usage Tracking

Just joined a company starting on rebuilding their product as a SPA and we are sadly lacking in any real metrics on feature usage. The product is a SAAS B2B where some roles in our customers create content and others consume it. So I'm more interested in understanding which product features are being used than more page-oriented stats on content views etc.

Looking for input: - on approaches to take to get feature usage metrics on SPA and how to analyse; - SPA moving to VueJS, any plugins recommended to just make it easy; - currently using Google Analytics (and some internal tracking when we audit API usage), any recommendations of significantly better services (SAAS or hosted)