We tell you what to do with the collected trash and garbage in the inventory.
The fact that you can sell garbage, you will learn at the very beginning. However, it will not be clear to whom and where. Each major settlement has several merchants. You can only sell weapons and clothing to a gunsmith or clothing vendor, respectively. They don’t buy garbage. However, there is a general goods vendor in the city. It is marked with a “cash register” icon. Approach him, examine the list of goods and hold G to sell all the garbage.