An altar... in mount Ebal... — This was explicitly commanded in Deuteronomy. The blessing was put on mount Gerizim, the altar and the curse on mount Ebal. We do not hear elsewhere of any sacrifice on Ebal. But it is certain that God accepted sacrifices in many places in Canaan. (Cf. Exodus 19:24.)
Related Commentaries of Joshua 8:30
Joshua 8:30-31
30 Then Joshua built an altar unto the LORD God of Israel in mount Ebal,
31 As Moses the servant of the LORD commanded the children of Israel, as it is written in the book of the law of Moses, an altar of whole stones, over which no man hath lift up any iron: and they offered thereon burnt offerings unto the LORD, and sacrificed peace offerings.