My Pi 2 with Jessie runs Minetest out of the box at 15 fps for a typical scene with trees. (You'll of course get a higher fps looking at the sky.)
I've seen a "1 fps" bug affect both Minetest and full-blown Minecraft, and it seems to happen when the OpenGL driver isn't properly configured. Run
sudo raspi-config and select the OpenGL driver with full KMS. Check that
dtoverlay=vc4-kms-v3d so that it takes effect on reboot. If that doesn't resolve it, try with fake KMS.
(Edit: If running BerryBoot, this is notorious for causing performance problems with Irrlicht and will not play well with the full OpenGL driver. For Minetest you may have to invest in a dedicated SD card and give up dual-booting.)
If the issue persists and you have a bit more time, rule out the usual concerns with
sudo apt update; sudo apt upgrade; sudo rpi-update
Once you have the lag bug gone, framerate is most visibly affected by drawing text (press F2 to disable chat / log), followed by the HUD due to its transparency and some text (press F1 to disable). Ironically, this means pressing F5 to view the FPS counter makes the framerate instantly drop, so I ended up tweaking
src/game.cpp to report stats to stdout instead. On the bright side, opaque objects like "Steve" (press F7 to change camera view) are not computationally expensive.
You might squeeze out a few more fps by with
enable_clouds = 0,
new_style_leaves = 0,
opaque_water = 1, or disabling fog (press F3), but most options have little effect on performance. In fact a Pi 3 runs Minetest at about the same quality.
OpenGL ES (Mesa driver with VC4 support)
It's worth noting you can compile Irrlicht for standard GLES and configure Minetest with
video_driver = ogles1. I have used these instructions, although for faster compilation and keeping enough RAM on-device I use clang instead of gcc. Also note: requires the
stable-0.4 branch of minetest.
However, the resulting configuration has slightly worse performance than full OpenGL. This makes some sense, given that it's much the same software rendering with limited VC4 acceleration.
OpenGL ES (Broadcom VC4 driver)
Besides the thread from 2015 you linked, there's this thread last updated in March. I have responded on the latter with instructions for building Minetest linked with brcmEGL + brcmGLESv2.
This performs significantly better than the Mesa GLES configuration, often 50+ fps with a fair amount of geometry in the scene. The same tuning tips apply as with OpenGL, although little things like text rendering can cause a more severe fps drop.
There may be further bottlenecks in Irrlicht/Minetest aside from rendering that could be identified by first building with
However, now that both minecraft-pi and PC Minecraft run faster on the Pi, that could be a reason Minetest is getting less attention.