Hi, You'll want the last Intel INF driver made for Windows 98 (ver 5.00.1012) for certain. The onboard audio is crap for Windows 98 and I highly suggest you grab a cheap Sound Blaster Live PCI. I'll check my files and see if I can determine LAN driver. I have built several Windows 98 retro PCs around this and similar i845 boards. They work well!
You're having such a hard time finding drivers because Intel decided to be asses and removed their entire back catalog of drivers/software/documentation/etc. for products older than 10 years in mid to late 2019. It's unfortunately an increasingly common theme among tech companies, HP obliterated their software archive some years before that, and other companies like Dell and AMD have been guilty of doing it too, but haven't wiped everything out. Creative has removed downloads for their oldest products as well. It costs virtually nothing to host said files these days, and the bandwidth usage is not going to be that much.
Thankfully someone scraped Intel's download server and managed to save 342 gigabytes of stuff before it went offline and uploaded it to archive.org. If you don't want to download the whole kaboodle, you can download specific files out of the archive if you know what you're looking for.