Today I run a k3s cluster with different boards: 5 Orange Pi PC2, 2 Rock64 (2G and 4G), a NAS with a Rock64 2G, 1 Jetson TX1, 1 Jetson Nano.
I have also other board in use: 1 Pine64, 1 Rasp Pi4, 1Rasp Pi 3, 4 Orange Pi Zero (H2 and H5) and an old Odroid XU3 Lite and 1 Odroid HC2.
I use Armbian on all of these where it is available. The Rasp Pi boards and the . All those boards were bought over the time from 2011 when I started with a Bifferboard and later the BeagleBoard.
On the cluster I run several services (from flight feeders to meteo station services, home automation and video surveillance and a STORJ node on the HC2.
The experience so far was quite good (thanks also to Armbian) especially with the Odroid HC2, the Rock64 and the Pine64. The Orange Pi (both PC2 and Zero) are more susceptible to HW problems; I had more PC2, 3 of them stopped working and now are broken but I can expect that being very cheap, so the manufacturing quality is quite low.
I would like to replace gradually the Orange Pi PC2 with a board that is more reliable and it seemed so far that the quality/price of the Rock64 has been quite good but it in the end it is more important to have a good OS on top of them. Ideally that "mighty" board should have good performance, low cost and Armbian well integrated with it. Minimum requirement is at least 4 core, 1 USB3 or SATA port and 2G of RAM. I do not like the Rasp Pi (due mainly to the software).
I do not know the reason of change of support for the Rock64 and so I asked about that.; considering the situation myself and another colleague were looking also to alternatives like the Odroid C4.