Opening Closed DMs without Sharing Any Sort of Connection + Silently
Let's say you want to open old conversations on someone you used to know. Mainly for potentially deleting any sensitive info you might have in there. This could have been 15 seconds ago or a few years ago. And you don't have any sort of way to open their profile UI. So, no mutual servers, not on your block list, not on a pending friend request, and the DM as mentioned is closed/not on your list. Additionally you don't want to have to send a friend request to get the UI open.
This sounds weird, but it makes more sense when anyone can have anything in their home as long as they want. Purely for just getting the UI to open it up.
Firstly, download your Discord Data Package and make sure to select Messages. (There is a chance you might actually already be on this step and saw some familiar usernames, with messages attached to those respective jsons) Once you get it, navigate to
package\Messages\index.json
Personally, what I like to do is replace every instance of ", Yes, double quote comma with a \n for new line. It makes everything supremely readable. You have a list of every id, and who/where it is from. You can natively search their username then to see if you happen to have a connection. DO NOT do this next step if you do. Please double check haha. You will be able to do what you need to then. Otherwise.
EDIT: I thought I mentioned it, but I guess not. You use the number in index.json. Go to the respective folder of the same name. Open up channel.json. Since we're looking for DMs. It will say type DM. In the recipients field, you will see the actual userids. Copy your own userid so you know what is yours and then put it in your memory it for later. You will use the other one for the command below.
Open Discord and go to any available channel. Type
/msg [userid] [literally anything]
The second part will spook you out because it seems like you're going to message them, but it will be completely unavailable. You can test this yourself, really. I did. I have an account that is completely wide open to DMs and using an alt I typed this in with nothing sharing with either. You will receive a Clyde error message that leads to an article. This is separate from message requests. It won't send that. Those are purely for when you do share a server with someone which we don't. This command skips that and is trying to send it as if you already know this person and putting it into the regular bar and hitting enter. The receiving user will not get any sort of notification.
Best of luck