Existing references I looked at before I went on trial and error until eventually I managed to make it work:
- https://gist.github.com/subrezon/b9aa2014343f934fbf69e579ecfc8da8 (the format of this gist copies this one)
- https://forum.openwrt.org/t/minimum-ovmf-uefi-folders-and-files-to-boot-openwrt-in-proxmoxve/75824
- https://forum.proxmox.com/threads/openwrt-boot.130221/
Note
Although links above were good references to look at so I didn't have to start from scratch, following none of them actually worked for me. Hence, I'm leaving my own note after figuring things out.
My situation:
