Google’s John Mueller said it several times before: if possible, do not use m-dot domains for your mobile websites. Better use responsive web design. John Mueller has just said it again:
Re:m-dot vs responsive/dynamic serving: I strongly recommend not using m-dot URLs if you can, especially with new sites. It makes everything so much easier. Re:PWA — they can do cool stuff quickly, but they're also hard to get right, especially for SEO (not impossible though).
— ? John ? (@JohnMu) September 27, 2019
How to do a mobile-first website audit
The website audit tool in SEOprofiler can check your website with a mobile user bot so that you get a mobile-first SEO website audit report:
