With regard to hydroxychloroquine (HCQ), there is nothing that could be considered definitive about its efficacy or safety for all people when used as an off-label treatment for COVID-19. While there is evidence that (in some people) is does not reduce the viral load ("Neither HCQ nor the combination of HCQ and AZTH showed a significant effect on viral load in any of the analysed tissues." [1]), there is evidence that HCQ "... can significantly decrease the production of cytokines and, in particular, pro-inflammatory factors" [2] and HCQ has "... potential, but controversial, characteristics to combat pathological inflammation associated with COVID-19." [3]
Of course, raw research does not give a definitive answer about efficacy and safety for all people, but it does suggest that HCQ may be one possible treatment (perhaps preventative, perhaps in vitro) for inflammation, which is one of the serious complications of COVID-19. It will likely be years before the mechanisms of COVID-19 are well understood. In fact, it is likely that some other urgent calamity will come along and compete for research funds currently used for COVID-19 research, which could significantly extend the time it takes to understand the SARS-CoV-2 virus.
[0] https://www.nature.com/scitable/topicpage/adaptation-and-phe...
[1] https://www.nature.com/articles/s41586-020-2558-4
Even more general reason to be sure that Trump was not right in his overt belief in chloroquine efficacy.