trixie recent update causing video instability

Following a normal trixie update two or three weeks ago, I have found that I 
have to reboot my main desktop machine every few days because the video 
becomes increasingly riddled with unwelcome artefacts as I use the system. The 
artefacts seem to be triggered, or at least made much worse, after watching 
youtube videos or using Google Streetview (in Firefox).

Linux video nowadays is a mystery to me, so I don't know what I might do to 
address the issue, and suggestions from those who understand these things 
better would be welcome.

Output from inxi:

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[ZB:tmp] inxi -SGaz
System:
   Kernel: 6.12.94+deb13-amd64 arch: x86_64 bits: 64 compiler: gcc v: 14.2.0
     clocksource: tsc avail: hpet,acpi_pm
     parameters: BOOT_IMAGE=/BOOT/debian@/vmlinuz-6.12.94+deb13-amd64
     root=ZFS=rpool/ROOT/debian ro root=ZFS=rpool/ROOT/debian
   Desktop: TDE (Trinity) v: R14.1.7~[DEVELOPMENT] tk: Qt v: 3.5.0 wm: Twin
     v: 3.0 with: kicker tools: avail: i3lock,slock,xss-lock vt: 7 dm: 1: LightDM
     v: 1.32.0 2: SDDM note: stopped Distro: Debian GNU/Linux 13 (trixie)
Graphics:
   Device-1: NVIDIA GF108 [GeForce GT 430] vendor: Gigabyte driver: nouveau
     v: kernel non-free: series: 390.xx+ status: legacy (EOL~2022-11-22) last:
     release: 390.157 kernel: 6.0 xorg: 1.21 arch: Fermi code: GF1xx
     process: 40/28nm built: 2010-2016 pcie: gen: 1 speed: 2.5 GT/s lanes: 16
     ports: active: HDMI-A-1 empty: DVI-I-1,VGA-1 bus-ID: 04:00.0
     chip-ID: 10de:0de1 class-ID: 0300
   Display: x11 server: X.Org v: 21.1.16 with: Xwayland v: 24.1.6
     compositor: Twin v: 3.0 driver: X: loaded: modesetting dri: nouveau
     gpu: nouveau display-ID: :0 screens: 1
   Screen-1: 0 s-res: 1920x1080 s-dpi: 96 s-size: 508x285mm (20.00x11.22")
     s-diag: 582mm (22.93")
   Monitor-1: HDMI-A-1 mapped: HDMI-1 model: VGA TO HDMI built: 2013 res:
     mode: 1920x1080 hz: 60 scale: 100% (1) dpi: 96 gamma: 1.2
     size: 509x286mm (20.04x11.26") diag: 584mm (23") ratio: 16:9 modes:
     max: 1920x1080 min: 640x480
   API: EGL v: 1.5 hw: drv: nvidia nouveau platforms: device: 0 drv: nouveau
     device: 1 drv: swrast gbm: drv: nouveau surfaceless: drv: nouveau x11:
     drv: nouveau inactive: wayland
   API: OpenGL v: 4.5 compat-v: 4.3 vendor: mesa v: 25.0.7-2 glx-v: 1.4
     direct-render: yes renderer: NVC1 device-ID: 10de:0de1 memory: 991.2 MiB
     unified: no
   API: Vulkan v: 1.4.309 layers: 3 device: 0 type: cpu name: llvmpipe (LLVM
     19.1.7 256 bits) driver: mesa llvmpipe v: 25.0.7-2 (LLVM 19.1.7)
     device-ID: 10005:0000 surfaces: xcb,xlib
   Info: Tools: api: clinfo, eglinfo, glxinfo, vulkaninfo
     de: kscreen-console,kscreen-doctor wl: wayland-info x11: xdriinfo,
     xdpyinfo, xprop, xrandr
[ZB:tmp]

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