Warning : The icon does not always appear despite completing the prerequisites for the next mission. If this happens, switch to another character, save in a safe house and switch back to Michael. The icon should then appear.
There are no objectives to complete so simply head over to the “?“ in Raton Canyon to begin the mission, then approach the red truck to trigger a cutscene. After the scene, you will find yourself out in Grand Senora Desert near a bunch of satellite dishes. After a while, you will receive a text asking for a donation and linking to Epsilon’s donation page.
Donate $500 to continue to the next mission. An Epsilon icon will appear on your map in Downtown Vinewood. It looks like a strange “E”.