Boot problem and install disk won't bring up anything but recovery

[Armoured]

My quite stable (for at least a year) z390 board had some kind of problem when I was out for a few hours, and the boot disk seemed to be hosed (data partition had unfixable errors).
I've tried everything I can think of including making a new install disk (with a known-good EFI), and erasing that boot drive.
Now with the install disk it simply will not boot up into anything but the macOS recovery, which didn't work before and no longer useful (since boot disk erased).
Any ideas?

 

[Armoured]

So, rather a nightmare day, but in the case this helps anyone:
-the problem I had getting stuck on recovery is a serious instructions issue: if the recovery screen comes up, it turns out you need (or I needed to) unlock a disk - any disk, even an unrelated disk - to progress to the next page, utilities, incl install macos, disk utility, etc. (I was worried that was going to change something and didn't and still doesn't make much sense to me why that step is necessary... since it works by unlocking an unrelated disk).
-then I had an issue with the installer choking and getting to 'an error occurred loading the update.' Pretty obscure and uninformative error.
-some intrnet sleuthing led me to testing the memory, using memtest86. That did indeed turn up some memory errors. Running further tests / swapping out memory as we speak before attempting to install again, but I've at least got it narrowed down to two of the memory chips (it seems).
-I've now taken out two of the memory chips (this is a system with 32gib, so 16g still manageable). I have now done a successful install. Will figure out what's up with the memory later and whether I really need /want to replace. It was normal memory, crucial, but not the cheapest out there. They've been good for three years or so - first time I've ever had memory just fail like this.

This is I guess another example that macos can be a bit picky about memory. Or possibly my memory just fried somewhow.