I don't know what goes here.
Devkitpro is a package that is a combination of the GNU-GCC development tools (
http://gcc.gnu.org/ ) with a lot of libraries made to do things for the consoles they care about and tools to further that goal (header makers, packing tools for ROMs, graphics conversion tools...).
It was originally made to work with the PC (and still has that as primary) rather than the ARM processors of the raspberry pi, however GCC gets ports to most places, libraries are text files and that mostly leaves the tools (which are largely open source as well, though open source does not necessarily mean trivial recompile on new platform even if I would expect most to not go too radical and be largely limited to baseline C libaries) and integration efforts (such as they are -- it is still real work done but compared to the likes of visual studio,
https://www.codeblocks.org/ , various other IDEs
https://www.educative.io/blog/best-java-ides-2021 and such then rather less) to be replicated if trying to get it going on for an ARM based version of Linux you presumably have on the pi. I am some years out of playing on raspberry pi linux but I imagine it is doing to be a debian base (raspbian) you are using which is probably for the best as it is likely to have the most things ported to it/available from standard repos over something more specialist like openelec.
For reasons unknown devkitpro a few years back went somewhat away from the typical free and open software approach of have any old version we have along with the source code to it (only reasons for not being if it bricks things unnecessarily or because it was lost by dint of being pre internet/everybody backs up everything), removed all existing source code snapshots, very aggressively went after anybody hosting old versions (to the point it hurt their rep quite a lot, though they are still the main game in town so...) and keeps things fairly tight/in house/use current version or get lost. This might be what you are running into if you are using an old take (2018 being an old take at this point) on porting it to a new platform and it is not up to date with the current approach to the world employed by devkitpro. Trying to replicate it might then be tricky if you don't know much about linux and presumably not much either about programming environments.
When asked above what happened that was for good reason -- the error codes generated will potentially tell us what failed to be ported over, what is missing, what libraries might be too new, and with that you can head down the path of replicating it, adapting it for newer versions and more besides. By all means try to sort if yourself -- it will probably leave you with a deeper understanding of both Linux and the GCC development environment (which Microsoft's Visual Studio is about the only thing that competes with it for biggest). However if you are trying to do this whilst also getting to grips with C coding then... it is not the worst and again will give you very useful skills in the end but is still jumping in at the deep end.
Your best options for ease then being hoping someone has a snapshot of their raspberry pi having done that which they are prepared to share (hopefully the DKP devs do no get uppity about it), or getting the old versions as it would have been in 2018 for everything (raspian or whatever was being used, possibly sort repos to be older versions if they have been archived, old devkitpro if you can but good luck on that one being available as source) and working with that. Otherwise prepare to learn things about Linux, development environments and compiling software beyond that which you might have been hoping to do to have a little play with GBA homebrew.