@Llumex, I do agree. I find myself having to kill Minecraft very often, and it really does annoy me. To know Minecraft has been having fullscreen issues on Linux for more than a year really does make me think this.
F3+T = Reloads current resource pack (will lag)
F3+S = I forgot what this does, but it is a resource demanding debug feature
F3+A = Reloads loaded chunks
All of these are intended to cause said lag spikes.
World Border in Nether = This might not be intended
This happens on servers that use the method of putting § in front of names. To re-create try servers like us.mineplex.com and mc.hypixel.com
@Llumex No, I don't have a lot of lag. Infect, I lag less on Ubuntu than I did Windows, as Ubuntu installed a driver for my GPU that can handle VBOs; the one I had before would crash my game whenever I tried to enable them.