To this day, I have yet to find a way to adequately install (or, ideally, clone from a kosher external drive) Mojave onto a "silverback"-era (2009-2011) dvd-model iMac, and by "adequately", I mean that ALL of the following have to work or be satisfied:
* audio enabled
* wifi enabled
* hardware-acceleration enabled
* video drivers work w/correct colors
* at-rest memory usage not greater than 3gb ram
* machine doesn't run hot
-- If anyone has discovered a procedure for these specific machines that doesn't require upgrading hardware, please post it.
I've used dosdude's patcher on some of these:
* audio enabled
> No problem with Audio for anything I've tried.
* wifi enabled
> No problem her either.
* hardware-acceleration enabled
> Depends on the GPU.
* video drivers work w/correct colors
> Depends on the GPU.
* at-rest memory usage not greater than 3gb ram
> I don't even get that on my Mac Studio. Mac OS has always been memory hungry. Every version requires more memory than the last (well, Snow Leopard may have been better than Leopard, but that's about it).
* machine doesn't run hot
> I've never used any metal Intel iMac that didn't run super hot on the back. This is even more true for anything that's running an OS that wasn't made to support the hardware. However, one of the functions of the aluminum chassis on all Macs is to drawl out some of the heat. That being said, Metal Intel iMacs are like tiny space heaters.
I may not be trying the specific models you are, but the patcher has worked great for me. The only exception is the AMD 5xxx / 6xxx GPUs. This is due to the fact that these GPUs have a lot of physical issues, and their drivers were difficult to get working, so between both of those problems, dosdude didn't want to put the extended effort into getting them working (if you were even possible).
One of the important things you need to do is go back into the patched installer AFTER the OS finishes installing, then run all the proper patches.
Also, it would be impossible to clone a vanilla install of Mac OS onto an unsupported machine, and get it booted without running the patches, as the patched drivers need to be installed. I have, however, cloned one won identical machine to another, and had no issues booting it. I've also cloned a vanilla install, then booted it directly into the USB patcher, ran the appropriate patches, and was up and running. I used carbon copy cloner to do this, and made sure the options were said to make a bootable clone. I don't remember specifically which computers I did this on, other than I know I've done it with a 2011 MacBook Pro. So there may be some issues regarding booting APFS on machines that didn't support APFS in firmware. However, Mojave can still boot HFS+.
Not sure if any of this helps you.