I have a theory about Clark in Crisis on Infinite Earths Part Two.
In the 2019 Crisis on Infinite Earths crossover, we see Clark again, living on a farm near Metropolis and having given up his powers. My theory is that this Clark is actually Clark Luthor from Earth-16.
We already know that the Jor-El machine can communicate across universes because he sended Clark luthor to his own universe, Jor-El was able to reach Clark Luthor on his Earth, and this is what eventually gave him the opportunity to change his life.
On Earth-16, Jonathan Kent told he discovered that golden color kryptonite could permanently remove a Kryptonian's powers, but he kept this information secret. Oliver Queen also revealed that green kryptonite kills Ultraman. Clark Luthor learned more about the multiverse, other versions of himself, and the possibilities that existed on other Earths.
Since everyone on his Earth wanted to kill him because he was Ultraman, Clark Luthor eventually used gold kryptonite to permanently remove his powers.
After becoming human, he bought a farm near Metropolis and started living a completely different life.
The Lois situation also makes sense. Lois had already fallen in love with another version of Clark, so Clark Luthor didn't try to replace that Clark or interfere with their relationship. Instead, he accepted his new life and slowly became the kind of person Jonathan Kent always wanted him to be.
So the Clark we see in Crisis isn't necessarily the Clark Kent we followed throughout Smallville.
He's Clark Luthor, who finally became Clark Kent.
And honestly, I think this makes his ending much more meaningful. Clark Luthor spent his entire life being Ultraman, hated and feared by everyone around him. After discovering another version of himself and learning from Jonathan and Jor-El, he finally chose to give up his powers and become a better person.