This page of the trophy guide for Far Cry 6 explains how to unlock the Hogar Dulce Hogar trophy. You'll get it for the upgrading any object to the maximum in any guerrilla camp (in the single player campaign). Step by step instructions are included below.
The description of this achievement refers to these guerilla camps where the camera switches to TPP view. These are Montero Farm from the Madrugada region, Patriotas Peak from the El Este region, and Camp Maximas from the Valle De Oro region. You will visit all of these locations along with making progress in the main storyline, and you can try to get the trophy in any of them.
Each of the rebel hideouts features a Construction Desk . This is where you can order blueprints from the foreman to place unique objects in the camp.
There are 6 possible blueprints in the game, with a maximum of two blueprints in any given camp.
Projects are paid for with common crafting ingredients (e.g. metal, gasolina).
Initially, a level 1 object will be placed, but to get the trophy you need to upgrade it to the highest level 3. If you hover over the round icon under the object name, you will learn about the types of materials needed for the upgrade and whether you have them. Always be on the lookout for new crafting materials as you traverse the game world, especially when exploring enemy military bases.
Purchasing the third level will unlock the trophy. You only have to upgrade 1 of the 6 possible objects in this way. You don't have to upgrade all structures in all three guerrilla hideouts.