swr-gc-inactive-keys.jsx

import { unstable_serialize, useSWRConfig, SWRConfig } from 'swr'
import { useEffect } from 'react'

const counter = {}
const gc = useSWRNext => (key, fetcher, config) => {
  const { cache } = useSWRConfig()
  const serializedKey = unstable_serialize(key)
  
  useEffect(() => {
    counter[serializedKey] = (counter[serializedKey] || 0) + 1
    
    return () => {
      counter[serializedKey]--
      if (!counter[serializedKey]) {
        cache.delete(serializedKey)
      }
    }
  }, [serializedKey])
  
  return useSWRNext(key, fetcher, config)
}

// ...

<SWRConfig value={{ use: [gc] }}>

If I understand correctly, you can access the cache as config.cache, instead of needing to call useSWRConfig?