People are voting me down but it’s mostly from misinformation. WSL runs standard Linux distributions, it’s the real deal, not an imitation or anything that could be considered bad. If you face issues with it it’s mostly because of a fundamental misunderstanding of the setup (for example the person trying to run systemd…), not because it isn’t a „real Linux“.
it runs a modified kernel in a VM and it makes some basic things like mounting suck and IO slooow
That's exactly what I mean by misinformed. WSL 2 isn't using a simple virtual machine the way it is generally understood. It is instead using a lightweight VM using Hyper-V, there is no booting time. IO in itself isn't slow if you move files to the Linux FS. What is slow is the communication between Windows <—> Linux filesystems.
Edit: regarding the custom kernel, you can create your own if you want, nothing is blocking you from doing so https://kumekay.com/compiling-custom-kernel-for-wsl2/.
Microsoft's kernel is also available on github: https://github.com/microsoft/WSL2-Linux-Kernel.