The steps are identical to compiling for normal Linux, because, well, Raspberry Pi runs Linux.
Only real difference is that you need to publish the package for linux-arm instead of linux-x64 for obvious reasons,
It is important to mention that building osu!lazer on your Raspberry Pi will take a long time. You have an option of doing this on your PC and copying the built files over. It will be much faster.
git clone https://github.com/ppy/osu.git
cd ./osu
git submodule update --init
dotnet restore osu.sln
dotnet build osu.sln
cd ./osu.Desktop
dotnet publish --self-contained --configuration Release --runtime linux-armsudo raspi-config > 'Advanced Options' > 'GL Driver' > 'GL (Fake KMS'). Press OK, Finish and Reboot.
you can get libbass from here
if you are on 32 bit raspberry pi os, you will need to grab the binaries from the hardfp folder.
don't forget to get the fx24 one too
After all these, just run the osu! file that is build in ./bin/Release/ Making sure you drop the libbass files first. After that, try running.
Since lazer has integrated OpenTabletDriver, you can just configure some udev rules, blacklist hid_uclogic and it will just work. Check out this page on that.
sudo apt install libsdl2-dev
Do not install libasound2-dev. if you did, uninstall it.
This is because recently, Raspberry Pi OS has added Pulseaudio, which buffers sound and this leads to latency. One way around this is to use pasuspender to launch osu which will suspend pulseaudio. Then in the osu!'s sound device settings, manually select an audio device you wish to hear the audio from.
Unfortunately, you will need an external sound card for this to work. I was not able to get a stable sound this way though the built in headphone jack or HDMI.