The official list of all available tracks can be found in the Trackmania Turbo Center by Ubisoft.
To play other peoples tracks on your PS4 do the following:
Using the PS4 Maps Overview you can explore the tracks and filter them to some extend. What bugs me is that you can not just sort by "Most played" or "Best rated" tracks. This leaves you with little options to find the most popular trackmania turbo tracks available.
Thats why i've build the Trackmania Turbo Track Explorer. It Allows you to filter tracks by any environment, style and length you like. All tracks can be orderd by "Most Played" or "Best Rated" to find the most popular trackmania turbo tracks available.
Yes. The whole list of Trackmania Turbo Tracks for the PS4, Xbox and PC can be found here on google docs as a spreadsheet
My main concern was to find the best user generated trackmania turbo tracks to play with some friends. I will update the list from time to time. If the Explorer gets used a lot i consider adding features like showing trending tracks etc.
The Track Explorer uses javascript to access a google spreadsheet and filters the data using the Google Visualization API Query Language