If you're looking for Lennart in Dragon's Dogma 2 you must be pursuing the Oxcart Courier quest. When you first arrive in the capital city of Vernworth, an oxcart manager called Donovan asks you to take charge of delivering a letter to Melve. If you've travelled anywhere by oxcart, you've likely realised it's about as safe as punching a griffon in the face, so Donovan wants to make sure his letter actually arrives.
The letter is addressed to Lennart, but if you're anything like me, NPC names in fantasy RPGs go in one ear and right out the other. It's especially frustrating since Lennart is a character you undoubtedly will have interacted with before. Well done if you remember him, I guess? Otherwise, here's how to find Lennart in Melve so you can deliver that letter and complete the quest.
Dragon's Dogma 2 Lennart location
If you've spent any length of time hanging around Melve, you've likely met Lennart; he's a gruff white-haired old warrior who gives you the Nesting Troubles quest where you have to toss explosive barrels at some Saurians on the opposite side of the river. You can usually find him wandering around the ruins near the entrance, or in the upper half of the village by Ulrika's house. He's easy to spot since he wears fur armour with a cape, carries a sword and shield, and has a damn fine moustache.
Simply speak to him and hand the letter across to complete the delivery. Depending on your affinity with Lennart and if you've done the other quests for him, this might be enough for him to give you the Meister's Teaching, Soldier's Code, which grants the Riotous Fury skill for those using the Fighter vocation. Now simply head back to Donovan in Vernworth to get your reward and finish the quest.