"donor clones could work though couldn’t they? Hypothetically without a single scientific piece of knowledge to back it up. A few extra matching people ready to go for those rich enough?"
They would "work" as well as any old organ transplant works, which is not much. They all get rejected eventually and all you end up buying for your pain, misery, and lowered immune system is a few extra years that end in gruesome ways.
If we are actually going to invest the monumental sums of money, time. and effort into creating clones for eventual organ harvesting, at the very least you would make them out of a special (single) engineered DNA that doesn't cause tissue rejection. Recognizing them as clones everywhere they go would also help keep them in line and alienate them (us humans vs them clones) etc.
You would also need to keep them in safe, sterile conditions so they would not be ruined for organ transplant. What stops NLMG clones from smoking 2 packs a day to ruin their health, fucking like bunny rabbits to catch a million venereal diseases, or eating & drinking everything in sight and ballooning to 200 kg with cirrhosis? It's not like they are saving themselves for a happy retirement.
And what if they kill someone and their DNA implicates the person they were cloned from?
These are just a few examples of the myriad problems and issues that need to be addressed in such a scenario. NLMG doesn't address any of them. Readers who can "gloss over" this kind of crappy SF writing can only be those who don't normally read SF and so are not aware of how creative the better SF authors are in realistic world building.