This full factorial trial is part of the RECONNECTED project (www.reconnected-project.eu). RECONNECTED involves a consortium of 11 European partners responding to global societal developments affecting mental wellbeing of vulnerable citizens. The project will offer a digital support system with culturally adapted and personalised intervention tools to various vulnerable populations that are understudied and difficult to reach with regular mental health interventions (i.e. youth, people with low SES, migrant populations, and older adults). The digital support system targets both individual and social factors simultaneously (i.e. mental health literacy, psychological resilience and social connectedness) to maximise health benefits. The main aim of this trial is to examine if personalised micro-interventions and social activation add wellbeing benefits to mental health literacy. The additional effects of personalised micro-interventions and social activation to mental health literacy will be tested through nine full factorial trials in nine European countries. The second objective is to evaluate whether integrating a machine learning algorithm into personalised micro-interventions improves the effectiveness of the personalised micro-interventions compared to the standard version. This analysis will be conducted using pooled data from the nine trial sites. The third objective is to conduct a process evaluation to assess the feasibility of the digital support system, including usability, perceived usefulness, overall satisfaction, potential unintended negative effects, and engagement.