Yes, you can do that, but keep trying for peer reviewed HI review articles

I believe the "systematic review" by definition doesn't mean avoiding citing technical reports!

A systematic review is an analysis of all primary literature that exists on a specific topic. ... Therefore, you should not use these in the data extraction process for your systematic review, except if it is a technical report of original research paper. However, you can definitely use the original research articles cited by technical reports. https://www.editage.com/insights/should-previous-systematic-reviews-and-meta-analyses-be-included-in-a-systematic-review

“A systematic review attempts to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question. ... Systematic reviews are also a type of journal article, published alongside primary research articles in scholarly journals. https://beryliveylibrary.wordpress.com/2018/03/13/systematic-review/

Kindly check https://www.ncbi.nlm.nih.gov/books/NBK209507/

Once you define your inclusion and exclusion criteria, I believe some of the technical reports can be included in the systematic review. Reports such as those from UN and WB are drafted by highly experienced scholars and I can confirm to you that these may contain very vital information for the subject matter under scrutiny. Best wishes

i think yes...but there should be some positive correlation between your peer article and technical report...if sometimes reverse happens...then under such situation perspective can change...i think technical reports are really to the point and crisp and articles can be written on any new and old ideas....