It's for Modern Sonic's version of a stage called "Last Haven".
Judging by the name of the stage and the tone of the song, if this is real, it's probably music for the game's hub world. "Last Haven" would be an incredibly fitting hub world name given the context of this game.
I saw this the other day but didn't post it because I wanted to see if it would be proven as a fake or just a fan-made tribute. However, nothing has come out to disprove it and the uploader claims it's real, while also being scarce on details about the song's context.
As for the song itself, I really like it. It has that "slightly somber but upbeat and hopeful" feel to it, perfectly fitting for a "Last Haven". And the instrumentation and pacing of the song just SCREAMS Tomoya Ohtani, who is the game's composer. It's so on point that it's difficult to think it could be fake, I definitely don't think it could be fan-made, as it sounds like it was played at an actual studio. The only possibility for it being fake is if it was pulled from an obscure anime OST or something and the uploader is just taking advantage of the lack of recognisability.
In any case, I hope it's real, because this is an amazing track.