What feature do you want to see added?

Please change the update URL from SpigotMC to Modrinth or Athion.
If you use snapshots, and you update daily, you have to go through spigot's bot verification just to click on external download to get to Athion.

Are there any alternatives?

I don't know if the update notifier has any concept of snapshots and stable releases but if it has, it would be a good alternative to link to Athion for snapshot versions and to Modrinth for stable releases.

Anything else?

Although this is just a minor inconvenience, I bet a good amount of people are annoyed by this too