How can I get a Windows 98 game to see its ISO in Wine?

Check what path Wine has actually assigned to the CD-ROM drive. In winecfg, the drive letter should point to the directory where the ISO is mounted, and its drive type should be set to CD-ROM. Mount the ISO before starting the game, then check that the files are visible through that same drive letter.

Some older games check for an optical drive or a particular disc volume label, not just the presence of the game files. If the mapping looks right and the game still rejects it, Wine may not be presenting the disc in the way this title expects.

CDEmu is worth looking into if the game needs a virtual optical device rather than a folder containing mounted ISO files. Availability depends on your Mint version and configured repositories, so check those first instead of following an old installation guide or adding an outdated package source. CDEmu also needs its system components set up, not just a desktop control app.

I'd try the Wine drive mapping first. It is a simpler test, and if the game is checking for optical-drive behavior, CDEmu is a more relevant next experiment than changing the game files.

A Windows 98 virtual machine is a reasonable fallback, but attach the ISO to the VM as its virtual CD-ROM device. A host-mounted ISO directory shared with the guest is not the same thing, and may not satisfy a disc check. The guest also needs to recognize its virtual CD drive.

Older Windows setups can take extra configuration, so this may be more work than Wine. If you go this route, first confirm the guest can browse the disc before installing or launching the game.