It works but runs slower than it should, maybe because of missing firmware; however nouveau still does something since it is faster than hardware rendering.

lspci -vvnnk

00:0d.0 VGA compatible controller [0300]: NVIDIA Corporation C61 [GeForce 6100 nForce 405] [10de:03d1] (rev a2) (prog-if 00 [VGA controller])
	Subsystem: Gigabyte Technology Co., Ltd C61 [GeForce 6100 nForce 405] [1458:d000]
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
	Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 22
	NUMA node: 0
	Region 0: Memory at f2000000 (32-bit, non-prefetchable) [size=16M]
	Region 1: Memory at e0000000 (64-bit, prefetchable) [size=256M]
	Region 3: Memory at f3000000 (64-bit, non-prefetchable) [size=16M]
	[virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
	Capabilities: [48] Power Management version 2
		Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
		Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
	Capabilities: [50] MSI: Enable- Count=1/1 Maskable- 64bit+
		Address: 0000000000000000  Data: 0000
	Kernel driver in use: nouveau
	Kernel modules: nouveau

glxheads

  Display:     0x5629bdd80110
  Window:      0xc00002
  Context:     0x5629bdda7ab0
  GL_VERSION:  2.1 Mesa 19.1.3
  GL_VENDOR:   nouveau
  GL_RENDERER: NV4C