The S10 line does not support 5g, but the S10 5g phone will. The s10 5g will be released on April 5th supposedly to Verizon wirless 1st exclusively, the slightly later to other mobile carriers.
5g is in its infancy, very little if any 5g coverage or 5g networks even exist! When 1st availible it will only be areas rated kn city blocks, so tg coverage minimal at best. Prices will vary, from what Ive read itll run you a additional 10.00 a month on your wireless plan.
All mobile carriers will offer 5g coverage in the very near future, but 5g coverage will be small and very limited dor a while.