I'm posting the same answer on both sites, because the questions are basically the same.
Personally, I am in favor of merging Linux Systems Codidact and Power Users Codidact, ideally by transferring the content from Linux Systems to Power Users.
The scope of Linux Systems is pretty close to a strict subset of that of Power Users; any question that is on topic on the former is very likely to be equally on topic on the latter, but there are questions that would be on topic on the latter that aren't necessarily on topic on the former.
By separating the two, we needlessly introduce confusion and separation; requiring of every poster to decide whether a given question should be posted on one or the other. Separating a subset of questions can make sense when there is significant traffic, but since we don't exactly have that luxury, we should start simple and, as with Software Development Codidact, perhaps later consider splitting the sites if the amount of traffic gets overwhelming for one.
There are some practical issues that would need to be worked out if the content from Linux Systems Codidact is merged into Power Users Codidact, which seems to me to be the more appropriate merge direction; for example, there would probably be some almost-but-not-quite-duplicate tags. However, Power Users currently has 143 questions, and Linux Systems 52, both in their respective Q&A categories; going through those even manually can probably be done in no more than a few hours. Even manual curation of the migrated content does not seem a big enough hassle to be an impediment to merging the sites at this point. Any existing links can be kept valid relatively easily since post IDs are global across Codidact; we won't have any case of two "post ID 42" to coalesce.