Comment 25 for bug 1805668

I suggest ditching u-boot or compiling it using rpi_3_32b_config and then enabling BCM2836 support in menuconfig. To boot the official server image on the Pi 3, you have to make a few tweaks first, which include disabling u-boot, updating the bootloader files, and adding additional firmware for WiFi to work. An official image with all of this done beforehand would be more simple. Considering that the original Pi 3 was released in 2016, Ubuntu Server should work on both the Pi 3B and 3B+/3A+ out of the box. It's a pretty easy thing to implement.

First, either the linux-firmware-raspi2 or raspi3-firmware package should be dropped. We don't need two packages that contain the same files. Secondly, whichever package remains should be updated to include bootloader files compatible with the 3B+ and 3A+. Thirdly, the linux-raspi2 kernel should be updated to a version that is still receiving updates because the version included in bionic is past EOL. Fourth, compile future versions of the generic ARM64 kernel with CONFIG_DMA_CMA=y so that this kernel is actually usable on the Pi 3. See https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1803206. That way, people can create Ubuntu images using GRUB2, u-boot, and the generic kernel.