Lately I've been experimenting with my emacs setup, which has led to a lot of extra ELPA (gnu and nongnu) requests. Unfortunately, ELPA is very slow nowadays, which makes experimenting inconvenient. Also, I don't want to contribute to the already high load on the official GNU servers.
Are there any "official" mirrors for ELPA? How can I activate them? If not, how can I activate and validate non official mirrors?