Snoke met Ben around roughly 15 ABY.

Can still work.

Snoke is confirmed to have trained at least one other apprentice before he became interested in Ben.

False memories, Palpatine is the one who trained and Snoke is lying, something something.

lso, Snoke had an advanced knowledge of the dark side, which (if he is truly a genetic creation here) he would have to have learned from Sidious or the Sith loyalists.

Implanted memories.

The creation of force-sensitive clones was already occurring for years at this point under the guidance of Sidious' new body and the Sith of Exegal.

This is easy to retcon. Maybe they were doing multiple works across places.

Your headcanon could become true! We don't know anything, and I love this feeling.