While not exactly what you're after re: DYI, the WHO has published guidance on home care for patients presenting while mild symptoms in addition to their clinical care guidelines:

- Home care for patients with COVID-19 presenting with mild symptoms and management of their contacts [1]

- Clinical management of severe acute respiratory infection when novel coronavirus (nCoV) infection is suspected [2]

- All WHO technical guidance [3]

[1] https://www.who.int/publications-detail/home-care-for-patien...

[2] https://www.who.int/publications-detail/clinical-management-...

[3] https://www.who.int/emergencies/diseases/novel-coronavirus-2...