One thing you can try doing is burning the discs on your Win10 machine at a slower speed, if you can. I have read in the past doing this can help improve the readability of burned optical media on older computers. Quick research suggests that switching to DVD+R probably wouldn't work since +R media apparently has more compatibility issues with older hardware, but it might be worth a try if you haven't already. You could also try burning CDs instead of DVDs, those tend to have better compatibility with pre-XP systems from my personal experience, but that could be a fluke based solely on the model/revision of DVD drive in the old computer.

If you have (or can get) a USB floppy drive and some disks, you can connect it to the Win10 machine and use that to copy the USB mass storage driver onto the Win98 machine, since it is small enough to fit on a floppy disk.

Old CD drives don't like burned CDs. To improve compatibility, burn them as slow as your burner allows you to.

This website http://www.win3x.org/win3board/index.php have some drivers available (including the universal USB driver for windows 98) and it works really well with old browsers (you can even use it in Windows For Workgroups 3.11 with IE4 !).

To get it online without any disk except the Windows 98 CD, a NIC from a good brand released before 1998/1999 should do the trick (like a 3com etherlink III ISA, a 3com Etherlink XL PCI, an NE2000 compatible NIC, an old intel NIC ...)

You shouldn't have any issues at connecting an old PC on the internet, old viruses are long gone, most websites won't even load, hackers aren't targetting these oses anymore and you I bet you won't store any critical data on here anymore.

The worst a virus can do to your old PC is to erase your BIOS, but your motherboard should have a jumper preventing any write to the EEPROM, just put it in the correct position and you should be fine. And if it's too late, it's still recoverable with an EEPROM flasher.

Nowadays, you're more likely to get virusses out of old floppy disks (I've met 2 or 3 DOS virusses on 5"1/4 floppy disks so far) rather than from the internet (0 virusses since at least the mid 2010's, and my computers get connected frequently)

OK I'll look for some cheapy CD's thanks.

Looking at the machine it does have a floppy drive but not on my Win10 machine, so 1/2 way there!

Thanks. How do I burn at a slow speed? It has been years since I remember doing it. Does windows have an option for that? Simple thing I know..

Use a custom CD burning program like IMGBurn and select the burning speed from there

IMGburn that was it! Thanks for the help.