Found a new way to do all of the above, you don’t even need to the video.

All you need is luci-app-aria2 plugin installed,

Then go back into the router config, going to More Settings > Advanced > then log in.

You’ll see a new tab called services, with Aria2 Settings in the dropdown.

All you need to do is select the enable checkbox and set a download directory. Then use webui-aria2 or ariaNG to access the web gui of aria.