Hey Neil,
I haven't used a stand-alone analyzer option in quite a while. I did check out the SurferSEO site and there's a testimonial from Matthew Woodward. I tend to trust his opinions and like his SEO methods.
I have a WP installation that isn't for public content with RankMath installed on it and use it from time to time for analyzing content.
https://rankmath.com/
You may want to check our RankMath and compare it (and the results you get) with SurferSEO.
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