Can it be used to seal cement floors indoors? And to seal the concrete driveway outdoors?

Yes, linseed oil can be used to seal cement floors. The oil or wax penetrates deep into the capillaries of the cement tile and hardens. Although this type of sealer is already quite stable, it does not provide an absolute stain stop. For this reason, you should refrain from oil and wax sealing in kitchens and wet rooms. However, in highly frequented areas such as corridors, shops where no liquids are traded, etc. oiling and waxing is definitely highly recommended.