Haha! It’s your lucky day 
thankfully I’ve been dilligent and keeping notes ever since I started tinkering with a RPi4, Proxmox etc. I went digging through these notes and found how I made a VM on Proxmox using the NextcloudPi LXD image.
If I’m not mistaken, or my memory is wrong, there is a couple that are looking for this information. I even kept snapshots
Now I don’t know if I kept notes of the entire process or not, there is quite a lot though but spread out over 2 or 3 txt documents, if I remember correctly …
I’ll put them in a new post