In Lemmy 0.19.4, there was an image proxy added that instances can use to preserve privacy. If your instance isn't using it, the above picture will be your IP. For instances that are not using the proxy, it's possible to attempt to collect IPs from just sending a message to users.
If you're attempting to promote an instance over using another instance, these might be helpful. They also work in comments.
They're really easy to write, this is a gist.
I had posted these previously in another subreddit, but never posted the source anywhere... and thought someone might find them useful.