Interesting to read that someone else is having this problem too.
It is been some 5-6 months since I struggled getting pre-release candidate of Lubuntu Lunar onto 32-bit EFI hardware. I never got the finger behind it (very unlike me), and at some time the problem ‘suddenly’ disappeared in a new daily pre-release.
After 10 days of learning, compiling, debugging Calamares and the rest, it suddenly worked on the daily pre-release, and not on the one pre-released a few days earlier.
And to be honest, I felt that I’d lost the battle, gave up. Lost interest too, and moved on. A few weeks after Lunar was released, I tried do do a clean install of the then released version on the same 64-bit/32-bit EFI machine…and surprise, surprise… it failed again.
It is hard to blame anyone specific for his. 32-bit EFI is an anachronism, the number of people using Lubuntu is not very large (I guess, but I don’t know). Other distro’s with LXQt that I’ve tested don’t have this problem. So…it could be some kind of unforeseen side effect of a specific software combination, grub, Calamares, who knows.
I’ve tested several distros, and it failed (on my 64-bit/32-bit EFI machine) only with Lubuntu. And as I said, at some point in time, the daily pre-Lunar did not have the problem (which already existed on the release before Lunar as well), and after a while the release of Lunar version did.
So I repeat myself, I gave up. I decided that it was not worth spending more time on it. The 64-bit/32-bit EFI machine got Debian with LXQt, and still works fine as an extra machine in my garden shed. I use it when I am outside and need to look up something quickly, when I am too lazy to get the “official” laptop from the house.
I have been having warm sympathies for Lubuntu for many years (since 2011 or so). And I still do, but I have to admit that currently I am not using it on any of my primary machines. I only use it (every day though) on a machine to read my mails. I’ve decided that for the foreseeable future I will stick with Debian and LXQt. Lubuntu is certainly in the gene pool. I will keep on checking out what’s going on in the next release.