I'm not sure if it is the right forum to ask the question .... There are a lot of devops certification proposed in the market, which one do you recommend (more global or "generalist" and not specific to a given "tool") ?
Like you already know, DevOps is a technology stack where you learn to use the different applications and a programming language 'on the job'.
This means that any and all DevOps certifications will only test your basic knowledge of certain techniques, methods and principles.
That said, If you want some certifications in DevOps, I would suggest Dasa DevOps and if you work/live in North-West Europe you could also/instead do the EXIN DevOps.