My NAS is a super simple setup: I have OpenWRT running on my router and a USB drive connected to it.
All I need to do to have this drive accessible on Windows 98SE/ME/XP/7 and 10 was to mount the harddrives filesystem by following this tutorial here:
https://openwrt.org/docs/guide-user/storage/u … ives-quickstart
After that I installed the luci-app-samba application which lets me create a network share from the webinterface just by checking some buttons and giving it a name - under the hood this is based on Samba 3.6.
This makes sure SMB1 is available on Windows 98, but it can also use the more secure SMB2 protocol on Windows 10 for the same share. It's all done over the webinterface of the router.
Samba3 can be installed on any computer that runs Linux, so it doesn't neccessarily have to be a router (although it's very convenient, because I need one anyway).
I was not able to get this working with Samba4, though - although that is indeed supposed to work with Windows 98, just not out of the box...