Berkeley Open Infrastructure for Network Computing (BOINC) is a grid computing platform that lets you contribute the unused compute power of your PCs and mobile devices to various research projects. The client software is available for Linux, Windows, Android, macOS and other platforms and it support GPU computing on NVIDIA, AMD and Intel GPUs.
The amount of compute power you donate is publicly tracked and you can compete in various leaderboards. My favorite project is SETI (the Search for Extra-Terrestrial Intelligence). Here’s the national leaderboard for Guyana for the SETI@Home project. Compute power you donate to SETI@Home is used to analyze data from radio telescopes all over the world looking for low bandwidth radio waves from space that could signal the existence of technology capable of creating such waves, which we assume would be developed by an extra-terrestrial alien intelligence.