First of all, thank you - I no longer get errors on "apt update" when I have the /etc/apt/sources.list.d/armbian.list content un-commented for my stretch systems. Much appreciated.
One thing I expected to get with this was package updates related to armbian versions, such as:
linux-dtb-next-sunxi/now 5.83 armhf [installed,local]
linux-image-next-sunxi/now 5.83 armhf [installed,local]
linux-libc-dev/now 5.70 armhf [installed,local]
linux-stretch-root-next-orangepiplus2e/now 5.83 armhf [installed,local]
linux-u-boot-orangepiplus2e-next/now 5.83 armhf [installed,local]
To be clear(er), I initially install with the Armbian 5.83 image (the last one with the 4.19.x kernel, specifically 4.19.38-sunxi). Then I apt update/upgrade. This had brought my earlier systems up to Armbian 5.90 with kernel 4.19.62-sunxi. But even with the stretch support re-added to the repo server, that is no longer happening.
It is likely I am confused about where those linux packages were coming from, and perhaps I'm splitting hairs about dealing with two old kernel versions. But I'd thought it was worth asking about.
Thanks again for the timely response
Kevin