How do I use catch2 just by cloning its repository and copying its src to my project?

I am trying to get catch2 running for a barebone project just to get familiar with it but so far I failed installing it in whatever sense possible. the catch2-git repository either points you to installing it together with cmake (via vcpkg (I cannot use MSVC and don't want to at this point) or points to some Ubuntu solution.)

I figured I should just download the catch2 files directly and put it somewhere locally, run my code then and include the .hpp directly:

#include "../../Catch2/src/catch2/catch_all.hpp"

Now the compiler (I use gcc and the code blocks ide) will find catch_all.hpp but tells me that it cannot include the headerfiles that are linked in catch_all.hpp (first include tries to include catch_benchmark_all.hpp):

...\Catch2\src\catch2\catch_all.hpp|25|fatal error: catch2/benchmark/catch_benchmark_all.hpp: No such file or directory|

The #include statement in catch_all.hpp looks like this:

#include <catch2/benchmark/catch_benchmark_all.hpp>

Now I would assume that one answer to my problem would be to make all the include paths inside the catch2 to be relative but is that really what they want me to do here? There must be a better way, no?

The GitHub page says:

Catch2 v3 is being developed!

You are on the devel branch, where the next major version, v3, of Catch2 is being developed. As it is a significant rework, you will find that parts of this documentation are likely still stuck on v2.

For stable (and documentation-matching) version of Catch2, go to the v2.x branch.

On the v2.x page there's a link to a standalone header file:

The latest version of the single header can be downloaded directly using this link