I dont know if anyone else has had this problem but when i got the note for the DLC a quest did not show up after that. My house is currently in Whiterun and i went to see the steward for the house but he only gives me the option of adding a childs room to my house.... wtf. I went to each steward at each hold and they told me the same thing every time, u can buy a house IN town but no plots....lol.
I also talked to the Jarl's.. Nothing! BLASPHEMY!
I have the exact same problem. I’m level 81, played close to 600 hours with the same Nord. I know what I’m doing when it comes to Skyrim, that’s all I’m saying. But, like you I have been to all the districts, spoken with all the Jarl’s, I have purchased all the houses in the towns and still no land offer. All I got when I first launched the dlc was a courier that gave me a letter from the orphanage and one from the steward of Whiterun saying I can buy a child’s bedroom. I’ve waited and waited a still NO joy.
Just to make sure everything was ok with the dlc I started with a level 9 character that’s only just stared his journey as Dragonborn and hey presto, letter from the Jarl of Falkreath wanting to svck my helmet.