You can rent a Valheim server from something like gportal, or you need to set up your own hardware to run what's called a dedicated server. There are tutorials for that online, just make sure they are not outdated.

You can create a dedicated server. Either host the game for 'free' on a cheap computer you have in the closet, or buy a third party hosting service.

I use a mini-PC with the following specs:

- Windows 10 Pro
- Intel Celeron J4125 2GHZ
- 8GB DDR4 RAM
- Intel UHD 600 (On Board)
- 120GB Adata SSD

Connected to Telus Fibre 150 up/down. Runs 9 players with very little issue. If I ever need to do stuff with it, I just connect to it using Remote Desktop, and make sure the server game files are updated to the latest version. I also do periodic back-ups of the world saves.

Also, instead of giving my players my external IP, I have my external IP integrated into a sub-domain name via adding an A record.