Adopting open-source software (OSS) tools in modern education underscores the critical need for usability research to enhance learning experiences. This study has two objectives: to identify the usability techniques used in e-learning OSS projects and to evaluate the usability of an OSS e-learning tool, the LMS Desktop Assistant. A systematic mapping study (SMS) addressed the first objective by reviewing four significant databases: IEEE Xplore, Web of Science, ACM Digital Library, and Scopus, covering 2005 to 2024. This search resulted in 53 primary studies, revealing usability techniques such as questionnaires, heuristic evaluation, direct observation, surveys, interviews, and feedback mechanisms. The second objective involved using the Direct Observation and Test Questionnaire to evaluate the usability of the LMS Desktop Assistant, following an iterative approach incorporating student feedback to refine the tool's interface and functionality. The study also identified the need to explore personalization and cultural considerations in OSS e-learning environments. The SMS revealed a growing interest in techniques to improve user experience within educational OSS platforms, offering insights for more inclusive and effective e-learning environments. The LMS Desktop Assistant evaluation also highlighted key usability improvements, reinforcing the importance of user-centered design in OSS. This research provides practical guidance for developing more user-friendly OSS platforms that contribute to advancing educational technologies. © 2025 Elsevier B.V., All rights reserved.