Compiling on Ubuntu 20.04 - fixesproto 6.0 error

[Leseratte10]

Hello,

I'm trying to compile the latest version of Dolphin (46b99671d9158e0ca840c1d8ef249db0f321ced7) on Ubuntu 20.04, following the instructions on the Wiki: https://github.com/dolphin-emu/dolphin/wiki/Building-for-Linux

I installed gcc-10 and gcc-11 (tested both), and I installed QT6.

When running cmake, this is the result:

Code:

-- Xrandr found
-- Checking for module 'xi>=1.5.0'
--   Package 'xfixes' requires 'fixesproto >= 6.0' but version of fixesproto is 5.0
CMake Error at /usr/share/cmake-3.16/Modules/FindPkgConfig.cmake:463 (message):
 A required package was not found
Call Stack (most recent call first):
 /usr/share/cmake-3.16/Modules/FindPkgConfig.cmake:643 (_pkg_check_modules_internal)
 CMakeLists.txt:539 (pkg_check_modules)

Am I missing a dependency? I installed all dependencies that were listed in the wiki.

Googling the error message I found a couple threads with similar issues but no solution (Example 1, Example 2) but not really a solution.

Is the Wiki page missing some dependency for Ubuntu 20.04? Or did I somehow mess up my system so that this no longer works?

EDIT: A freshly-installed Ubuntu 20.04 prints this instead: 

Code:

-- Checking for module 'xi>=1.5.0'

--   Found xi, version 1.7.10
-- X11 support enabled

So I did probably mess up my system somehow. Does anyone have an idea how I can get it back to a working state? "xi" isn't really a name that one can google ...