Wood veneer is not hardwood, hence the treatment could be different from normal wood. They are sheets which is laminated on top of other wood.

What do you want to protect it from - water? Termites? Scratches? This would decide what you can use to protect it ...e.g. linseed oil, water based protection, natural oils, wax, etc

I know what you need to achieve. But to achieve what you want, you need to understand the thing you trying to protect. Wood veneer is is merely a layer of thin wood. It is not solid wood. Veneers are already treated with water-resistant properties.

If you want to further protect it, I would recommend a thin coat (or maybe 2, max) of lacquer.

Forget shellac. These are coloring from the lac bug found on trees. You will never get a consistent color from 2 different bottles. Imagine your cabinet have different tone of color... yucks.

Oil, or namely mineral oil is not a permanent protection. It has to be reapplies every few months 3-4 months. You sayang the cabinet now coz it is new. You rajin go oil it now. I see you still rajin after 1 year or not laaa. Anyway, mineral oil is for use to protect such end-grain cutting board.

You can refer to this site for the different types of wood protection.  Some of these brands can be purchase at Houz Depot, Kota Damansara or some decent hardware stores

https://www.ewarehouse.atkc.com.my/paint/wood-care

Linseed Oil is a bit challenging to find in Malaysia.

Wood itself is a very difficult thing to retain it as original form for the long time. When is dry, is getting lighter colour, when wet is become darker, so when you apply something, that must make the wood become darker, usually they will use lacquer, but that still will make wood become darker.

If you really like that original colour, maybe you can think of give up veneer and using High Pressure Laminate with that colour. Anyway, still not sure what you going to do for that veneer.

If its veneer, why need to add an additional layer of protection? Should already have something applied from the factory, its not raw timber.