To unleash the great potential of the Internet of Things (IoT), it is critical to facilitate the creation and operation of IoT systems across IoT, edge and cloud infrastructures with vast heterogeneity, scalability and dynamicity. What is the current landscape of the existing approaches and tools that attempt to cope with this complexity? The work presented in this paper contributes to this picture. This paper presents the results of our systematic literature review (SLR) on research approaches and tools for the deployment and orchestration of IoT systems (DEPO4IoT). From thousands of relevant publications, we systematically identified and reviewed seventeen (17) primary studies for data extraction and synthesis to answer our predefined research questions. The results of our SLR show the technical details of the primary DEPO4IoT studies. A main finding is that most approaches do not properly support software deployment and orchestration at the tiny IoT device level. Moreover, there is a lack in terms of properly addressing the trustworthiness aspects in approaches for IoT systems deployment and orchestration. In this paper, we suggest some potential research directions to address the gaps found.