Works only in 640x480, with and without KMS. Xorg works only after adding fbdev or vesafb in xorg.conf.d

lspci -vmmnn

Slot:   05:09.0
Class:  VGA compatible controller [0300]
Vendor: S3 Graphics Ltd. [5333]
Device: 86c375 [ViRGE/DX] or 86c385 [ViRGE/GX] [8a01]
SVendor:        S3 Graphics Ltd. [5333]
SDevice:        ViRGE/DX [8a01]
Rev:    01

lspci -vvnnk

05:09.0 VGA compatible controller [0300]: S3 Graphics Ltd. 86c375 [ViRGE/DX] or 86c385 [ViRGE/GX] [5333:8a01] (rev 01) (prog-if 00 [VGA controller])
        Subsystem: S3 Graphics Ltd. ViRGE/DX [5333:8a01]
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
        Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
        Latency: 64 (1000ns min, 63750ns max)
        Interrupt: pin A routed to IRQ 10
        Region 0: Memory at f8000000 (32-bit, non-prefetchable) [size=64M]
        [virtual] Expansion ROM at 000c0000 [disabled] [size=128K]

glxheads

  Display:     0x1ee8d20
  Window:      0xc00002
  Context:     0x1efcab0
  GL_VERSION:  3.1 Mesa 19.1.1
  GL_VENDOR:   VMware, Inc.
  GL_RENDERER: llvmpipe (LLVM 8.0, 128 bits)