The solution (more like a workaround, but still) is to open the Settings, press All Settings, open the Server / Singleplayer branch and doubleclick the Serverlist URL option to change it.
I don't know many alternative reliable serverlist options for Minetest. I've tried two serverlists:
- MultiCraft's serverlist (servers.multicraft.world)
- Minetest.net's serverlist (servers.minetest.net)
Sadly, the 1st one (MultiCraft one) doesn't work with Final Minetest.
The 2nd one (Minetest.net one) does work (attachment as a proof), but it doesn't show minetest.io servers, such as Moontest, Skydoom or Woofworld. But it does fix the problem nonetheless.