Adobe's EOL Matrix https://helpx.adobe.com/support/programs/eol-matrix.html
does not provide the end of life information for Robohelp 2017 and unless Robohelp Server 9/10/11 and Robohelp 2017/19/20 are the same thing I never got the notice. No one from Adobe Support was able to answer this question for me.
Nope, RH Server is NOT the same thing as RH - if it isn't mentioned in that matrix, then it's not EOL-ed yet. I don't think you were talking to the RH Support folks - they would have told you that. See https://helpx.adobe.com/contact/enterprise-support.other.html#robohelp for your support contact options.
Adobe responded. Essentially, there is no specific documentation or webpage that states EOL information for Robohelp. Only that the 2019/2020 are the only supported versions shown from the link below: