All ores in in crypts and or dungeons donot respawn, the solution is to find another seed for the ores and everyone simply logs into it from your server.
That seed will stay in your seed loadingmenu use a few different seeds. Log out with your ores in inventory then log into your main gain. You keep the ores.
Use this world seeder and tick the boxes. copy the seed , you start it then invite your friends. Not sure how you'd go about it on a dedicated server probably the same. I even have a seed unique for all the bosses so I dont get swarm attacks on my promary base. Good Luck
https://valheim-map.world/?seed=yfAXGazzJl&offset=-330%2C184&zoom=0.297