Sorry, couldn’t help myself! Seriously speaking though Pacesetter games have just released a 5e version of Into the Unknown which Pacesetter describes as:
Welcome to a world of new adventure! The day has finally come. Your training at Farrador Keep has come to its end. You are now a fully-fledged adventurer ready to make your name known in all the lands. However, this time, you will go it alone. Farrador is a relatively peaceful region; however, menacing monsters reside in the shadows of even the brightest lights. You are being called to explore abandoned mines, save villages from devastating foes, and claim your name as the next true adventurer. All this and more will be possible as you go Into the Unknown!
Into the Unknown is a true solo adventure for characters level 1-5 for the 5th Edition game system.
If you aren’t interested in 5e, there is also a version for BX and Frog God Games Swords & Wizardry (which as it happens is the copy I just ordered!) Links to all are below.