Is the CPU of Samsung Galaxy A10s 64 bit or 32 bit?
As suspected by OP, the hardware is 64 bit but it is running in 32 bit mode as mentioned in this reddit which in turn refers to geek bench for proof.

Apps like AIDA 64 can reveal this 



Source 

Also Antutu, if you have it installed, as it is removed from Play Store 

As general info, see How to find ARM processor version on android device?