As others pointed out, finding Win98 drivers for that will be quite a challenge. The same probably applies to Windows 2K/Me. If for some reason you don't like XP, a good alternative for T43 is OS/2 based OSs, starting from 0S/2 Warp 4.52. I tend to prefer supported and maintained software as long as the device is expected to surf the internet, so ArcaOS would be a better alternative.

Linux support for 32-bit x86 is shriking day by day; at this point you'd better install NetBSD on anything i486 onward (but this is just my opinion).

It's my OS of choice, and the with the passing of time I eventually installed it on most of my hardware:

• Thinkpad T460 (amd64), my current daily driver. HW probe
• Thinkpad R51 (i386), for retrogaming: dual-booted with FreeDOS
• Mac Mini G4 (macppc), for fun stuff and as DLNA.
• Workstation (custom build, triple-booted with Windows and Slachware; HW probe) . Mainly used for development and building packages
• Raspberry Pi4 (evbarm64), my main server (web, ftp, nntp, mail, matrix, git)
• Raspberry Pi3 (evbarm64), secondary server (firewall + DNS)
• SDF and tildeverse (tilde.pink)

I always wanted a SPARC machine but never got one.

AFAIK there's no support for Optimus graphics on *BSD unless either of the 2 can be kicked out through the BIOS. I'd give an attempt to disabling nouveau/nouveaufb on boot.