​So... in Speedrun rules category there is a sentence, that "Your video MUST start with the difficulty display (normal, hard, etc.) screen before the intro cinematic of the heist and end after showing the results page with the final In-Game Time (IGT)." However, in Solo mode, the difficulty screen and cinematic play only once, on the first attempt of the heist(if i am correct).

So, are runs in Solo mode allowed?

Yes, they are allowed. We will update the rules and leaderboards very soon!