If you wanted to go overboard, don’t even make the server accessible publicly. Distribute keys to a Wireguard network that is accessible publicly. Mandate your players obtain keys from you to play.

Veracrypt. Make a file on your disk.

Don’t want a storage file?

Make 2 partitions, put veracrypt portable exe on the first normal storage partition. (fat32 is likely ideal here) Second partition formatted with veracrypt.

I transcode to ramdisk.