Preferences regarding cleaning/protecting products for fretboards seem to differ drastically. Everybody recommends something else. Because I didn't want to spend much time informing myself, I just went with one very common product: The Lemon Oil. I bought it for cleaning my mint Yamaha Strat and kind of regret using it. The fretboard was a sticky mess afterwards and the stuff wore off very slowly. I rubbed the fretboard any time i changed strings with a soft towel. I had to clean my fingers every time after playing the guitar. And now, after some months, I got rid of almost all the sticky residue. Maybe I overused it in the first place, but that should not happen under any circumstance.
In my opinion, scraping the fretboard clean with a credit card is a much less harmful way of cleaning a guitar. There are also non-aggressive cleaning sprays out there (also on Thomann) that should do the trick too. I think that the need for protecting a fretboard is a myth and you should buy products that focus on the cleaning aspect only.
I also read of chipping wood when using Lemon Oil and similar products, but i didn't experience that. And to be honest, the Lemon Oil did quite a good job at wiping away the grease on the fingerboard.
