Start the game back up and you will be able to continue your community just before you started the final mission, with the corresponding achievement recorded. Upon selecting this option the game will close. You want to Select the option of 'Delete from console'. A window will appear stating you want to delete your save data for State of Decay 2. Scroll down to 'Saved data' and navigate to your profile name and select it. Wait for the legacy goal achievement to pop (mine popped on the load screen after the mission) then press then on State of Decay 2 game in your game tile, then select 'Manage game & add-ons' Arrive at the final goal and this time select 'Yes' and complete the final mission. Continue your game from the main menu and trigger the final mission (this usually takes 5/10 minutes of waiting around in game to cause the trigger). Select 'Not Yet' and exit to the main menu to force an autosave. Upon reaching the final mission (figuratively and literally, you will need to reach the final mission location) you will get a pop up which states your community will permanently end when you complete this mission. Destroy all plague hearts in your community and begin the legacy goal quest for your chosen leader and continue to the final mission. Cloud saving IS required for this method to work and each step detailed below is necessary.

Please comment below if you run into any issues. Please note, I have tried this method and it does work. Note: this method WILL make grinding out the 10,000 zombie kill achievement longer as you are not spending the time needed on a new community and in theory not spending the time mowing down zombies to get your tally up

It will still take the time to find all four hero types (Sheriff, Builder, Warlord and Trader) but you will not have to destroy all the plague hearts or rebuild your community from scratch each time.

There is a method for completing all four legacy goals in a single community rather than restarting your community after each legacy (you know, as the game was intended).

State of war full game