Perhaps Rivatuner can help out here? I haven't used this tool for ages but I remember it had various options like tuning LOD-bias. Perhaps/probably it had mipmapping and filtering options, too.

I am not sure what "authentic experience" are you looking for.... Pretty much any 3D accelerator supports bilinear filtering, even very old ones - Voodoo Graphics, Riva 128, etc. Perhaps early Matrox, ATi Rage and S3 Virge doesn't, but these have serious performance issues with most games as it is.

Rivatuner should be able to force nearest point mode. Apparently it was available on GF4 Ti and 30.x drivers http://ixbtlabs.com/articles2/gf4/gf4ti4200-3.html
I don't have the option on GF4 MX and 71.89 drivers, so at some point this function was dropped.

WRT "more authentic experience":

If you force disable bilinear filtering in many games, you'll also wreck the lightmaps that get blended and that's definitely NOT what the artist intended nor is it "authentic". Forcing nearest will also not undo the non-power-of-two textures getting quickly rescaled/resampled with detail loss or additional aliasing.

You'll also notice in the software renderers for the UnrealEngine1 games, there's intentional attempts at texture filtering anyway! The late '90s pc experience WAS about the bilinear filtering. If you were playing 3d accel'd PC games without bilinear at that point, you were probably on a Mystique or a PCX1 and there'd be much worse rendering issues (no blending functions).... or it's one of those few PSX ports with bad reviews about it.

on top of all that, 3dfx cards were common and they smeared the image output!

If you want to stick with chunky pixel 'authentic experiences', just prefer the software renderer if they're available. Not every 3d game was Darwinia

EDIT: here's a PCem 3dfx V3 screenshot with the emulation's filter forced off as an example of UT on nearest. Softdrv doesn't look like this either as that filters the luxels in the texturing.