Firstly I don't think you would like a random interlinking process, selecting random keywords and linking them to random posts, firstly because it won't do a shit, so better leave it even without links at all.
So automatisms on this topic is kind of tricky. First you need to let the algorithm understand which keyword would be preferred to be linked to each subpage.
Although you could leave this fully on autopilot, for example by using an AI API and telling such API to discover which is the most prominent keyword for each article and set it automatically, this definitelly is not implemented by any software I know so far.
Secondly once you have "discovered" (or you took the time to set which keywords are relevant to each article) then it will be time for the interlinking process.
There are plugins like this which simply rewrite posts on the fly on load with the keyword-page association you previously made.
In conclusion: unless you pay a dev, to make an AI automation analysis to discover keywords and alleviate your keyword selection process per post basis, you will have to do this manually. Sometimes if you use certain SEO plugin like rankmath or Yoast, you select the keywords in their SEO boxes. If you have developing knowledge (or you can hire a dev), he could extract such keywords and use them for this protocol also.
