Thank you all to those on the Development team as well as other contributors. Updating my R7800 from 18.06.4 to 18.06.5 was flawless.
Just the usual update image with save settings checked rebooted into 18.06.5 and then ssh in and then just put my packages back and reestablished /root symlinks:
opkg update opkg install kmod-usb-storage kmod-fs-f2fs block-mount rsyncd luci-app-sqm reboot ln -s /mnt/sda1/dotprofile .profile ln -s /mnt/sda1/dotvimrc .vimrc ln -s /mnt/sda1/inputrc .inputrc
Everything seems as expected.