This is on the latest neon downloaded yesterday... I'm attempting to install using the manual partitioning option, where I have previously created a partition /dev/neon-vg/rootlv.
The installation fails on attempting lvcreate on /dev/neon-vg... why attempt to create a volume group that already exists? Further more the logical volume /dev/neon-vg/rootlv is deleted after it's done.

I think my old, successful installation a few years ago was done similarly, although it's a bit long to recall for sure.

I find I am able to get past this problem by creating filesystems beforehand, in addition to just partitions.

Still no ultimate joy however, as the installer bails on grub failure. Shouldn't grub installation normally be optional? After all, this system already has a working grub I could continue to use.