Playing lands with Ugin's ultimate
You can put lands onto the battlefield with Ugin's ability because you are not playing lands (a special action limited to once a turn) you are just putting them onto the battlefield.

115.2a Playing a land is a special action. To play a land, a player puts that land onto the battlefield from the zone it was in (usually that player’s hand). By default, a player can take this action only once during each of his or her turns. A player can take this action any time he or she has priority and the stack is empty during a main phase of his or her turn.
305.4. Effects may also allow players to “put” lands onto the battlefield. This isn’t the same as “playing a land” and doesn’t count as a land played during the current turn.