To be more precise:
- Aside of some very old SBCs which never had any mainline kernel integration done, only on Raspberry Pi, RK3588 SBCs and NanoPi R5S/R5C we use a vendor kernel currently.
- Since we use Armbian’s “current” kernel builds in most cases (not on RPi and x86), we switch to mainline kernel once they do with their “current” builds.
I assume that ELEC distros have best Kodi performance. Those are highly tailored distros with a minimal OS around Kodi and they have a large community that only deals with Kodi (obviously). So they should be fast in switching kernel sources whenever one is found to perform better, or updating GPU drivers, e.g. if Mesa outperforms the vendor drivers at some point. But this is an assumption, while I have never used or benchmarked any ELEC OS.
Compared to most other Debian-based distributions, DietPi has a much lower foodprint indeed, but as long as Kodi is executed the same way (KMS/DRM/GBM vs X11), same kernel, GPU drivers and graphics APIs, once shouldn’t notice a real performance difference (on modern SBCs where some MiB RAM or some percent CPU usage once in a while more or less do not matter).
I’m no big fans of those vendor GPU drivers (like the Rockchip Mali blobs) which were always a pain to maintain the needed a constant testing and benchmarking effort to know whether and on which Debian version (Mesa version) and which kernel they actually do perform better, so over time I removed dealing with them completely in dietpi-software. So OOTB it will be always Mesa drivers, which do work quite well for older and widely distributed SoCs (RK3399 and alike). On newer SoCs, newer Mesa drivers are needed, often newer than what current stable Debian ships, e.g. Mesa 22 for good RK356x (Quartz64, ROCK 3A, NanoPi 5 series, …) performance. In this case using our Bookworm images or upgrading to Debian Bookworm makes a huge difference. For RK3588, AFAIK Mesa 23 is needed for good performance, which is currently in Debian “experimental” and hence will most likely not be shipped with Debian Bookworm (when it’s released). There is a PPA which can be used to install Mesa 23, some extra firmware blobs and GUI software builds which make use of it: Orange Pi 5 Hardware Acceleration enabled? - #2 by MichaIng