Slightly sensationalist title, apologies, but I posted this is in Chat yesterday with no replies and I thought others might like to join in.
Imperial College (along with some money from Voadfone) developed an app which uses spare phone capacity to help run calculations from it's super computer. It was initially developed to find cancer cures, but a few days ago they added a new project to find treatments for COVID-19.
It's called Vodafone Foundation Dream Lab.
All you do is download it, pick the project you'd like to support, plug your phone in and leave it. Make sure you're connected to wifi.(there's a setting to prevent the phone using mobile data too)
Link to Imperial College article that explains it better than me:
www.imperial.ac.uk/news/196733/new-covid-19-project-will-power-smartphones/