Ubuntu is nobody's favorite at this point. Inertia is pretty much all it has going for it.
I can see the applications being updated but I can't imagine how (or why) they would update the OS itself (unless they've been amassing service packs all along).
Microsoft has made a whole lot about the value of updating to improve security from external threats (that shouldn't be an issue here) but there are more active/unpatched bugs in Windows 10 or 11 than there ever were in Windows 98. Absent Microsoft networking and Internet access, Windows 98 (especially SE) was very stable.