Is there something better than mineral oil for cutting boards?
"Better" might be a matter of interpretation. The oils will behave a bit differently, however.

Mineral Oil is a non-drying oil, which means that it will not polymerize (form a plastic-like substance) over time. This is good for oiling cutting boards because it will stay a bit liquid in the wood and flow into cracks and scratches. It is also food-safe and won't go rancid or support microorganisms.

Linseed Oil (AKA Flaxseed Oil, or Flax Oil) is also a good choice, for a different reason. Linseed Oil is a drying oil, which means it will fully polymerize and form a harder plastic layer. This is why it is about the best oil for seasoning cast iron pans. It may be more durable than mineral oil, but lacks the ability to "flow".

A blend of the two sounds like a fine idea. My favorite, Howard's Butcher Block Conditioner is a mix of Mineral Oil and natural waxes like Carnauba and Beeswax, which add a bit of that "durability" that Linseed Oil could add.

What would be a bad choice are most food oils like Canola, Olive Oil, Lard, etc. Unsaturated fats will oxidize (go rancid) and affect your food. Even oils high in saturated fats may have too many anti-oxidants (which are bad in this case), which will prevent polymerization and leave a gummy surface. These semi-drying oils are of no use here.

Whatever you use, make sure it is intended for food (Linseed Oil is a common woodworking finish, and not all versions are intended for use with food). Mineral Oil is probably more convenient for quick daily wipe-downs, while some of the blends are probably a bit more suited toward occasional re-finishing. Either way, regular application and keeping the board dry while not in use will make more difference than the exact type of oil.