There is a conference that my supervisors and I have agreed to submit a paper to however, I am looking for alternative conferences (ASPLOS) that are similar to it. When I search the conference on ACM, I cannot find a "related conference" tab so I cannot be sure what conferences are related to it. My paper intersects the topic of software engineering and systems. Do you know of any conferences related to it ASPLOS or related? Or how to search for related conferences?
The easiest to search for related conferences is to look at citations of and for articles published in ASPLOS. This will give you access to papers, many of which might have appeared in ASPLOS itself if the authors had submitted there. Scholar Google will make this simple. You pick something to start with that is close to your putative submission. Another way is to look at people who are regular ASPLOS authors and look at their CV, though of course, even good people get rejected for ASPLOS.
ASPLOS is a bit peculiar and it is of course quite prestigious. The best alternatives will depend on the content of your paper and you should keep this in mind.