I imagine this must have been asked before many times but I cannot find a definitive answer for this:
How can I make all the links in my articles have the rel=“nofollow” attribute?
I understand that there is a Blackfriday option for this, but it seems it is not exposed in Hugo according to https://gohugo.io/getting-started/configuration/#configure-blackfriday.
Can indeed be interesting if that option is available in Hugo. Did you make a GitHub feature request for it? (Couldn’t find it.)
Have bookmarked this thread, hoping for an answer. For those setting “hrefTargetBlank” to true, it will be very useful to also be able to set “nofollow”, “noopener” and, sometimes, “noreferrer” to “true” for all external links.
Seems useful. Please make a github request for it to be enabled.
Since I could really use this feature of rel=nofollow on external links, but couldn’t find a GitHub issue, I made one here:
Add a BlackFriday option for rel=“nofollow” on external links.
If you find that feature request useful, please give it a thumbs up. A comment like “+1” creates a bit of noise since people like Bep and others might get a GitHub email for every comment, from what I understand. So it’s cleaner to use the 
feature on GitHub. 
I can see it got merged but im unsure how to activate this in my site.
Is this some thing that needs to be built into the theme?