This is concerning that after all this time (2,5 year) this issue is still here.

I have the same issue shown in journalctl. I believe it wasn't there from the start but showed a while ago. I don't see any problems on the frontend site, however.
I have a hybrid GPUs and currently use optimus-manager to switch between GPUs. Nouevau is making the switch (successfully).

Here is the bug:

nouveau 0000:01:00.0: bus: MMIO read of 00000000 FAULT at 022554 [ IBUS ]

My laptop is:

System:    Host: alienware-PC Kernel: 5.2.13-1-MANJARO x86_64 bits: 64 compiler: gcc v: 9.1.0 Desktop: KDE Plasma 5.16.5 
           tk: Qt 5.13.0 wm: kwin_x11 dm: SDDM Distro: Manjaro Linux 
Machine:   Type: Laptop System: Alienware product: Alienware 17 R3 v: 1.7.0 serial: <filter> Chassis: type: 10 
           serial: <filter> 
           Mobo: Alienware model: 0GH72M v: A00 serial: <filter> UEFI: Alienware v: 1.7.0 date: 01/18/2019 
Battery:   ID-1: BAT1 charge: 95.8 Wh condition: 95.8/96.0 Wh (100%) volts: 17.3/15.0 model: COMPAL PABAS0241231 
           serial: <filter> status: Full 
CPU:       Topology: Quad Core model: Intel Core i7-6700HQ bits: 64 type: MT MCP arch: Skylake-S rev: 3 L2 cache: 6144 KiB 
           flags: avx avx2 lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx bogomips: 41488 
           Speed: 933 MHz min/max: 800/3500 MHz Core speeds (MHz): 1: 900 2: 900 3: 900 4: 900 5: 900 6: 900 7: 900 8: 900 
Graphics:  Device-1: Intel HD Graphics 530 vendor: Dell driver: i915 v: kernel bus ID: 00:02.0 chip ID: 8086:191b 
           Device-2: NVIDIA GM204M [GeForce GTX 970M] vendor: Dell driver: nouveau v: kernel bus ID: 01:00.0 
           chip ID: 10de:13d8 
           Display: x11 server: X.Org 1.20.5 driver: modesetting compositor: kwin_x11 tty: N/A 
           OpenGL: renderer: Mesa DRI Intel HD Graphics 530 (Skylake GT2) v: 4.5 Mesa 19.1.6 compat-v: 3.0 direct render: Yes 
Audio:     Device-1: Intel 100 Series/C230 Series Family HD Audio vendor: Dell driver: snd_hda_intel v: kernel bus ID: 00:1f.3 
           chip ID: 8086:a170 
           Sound Server: ALSA v: k5.2.13-1-MANJARO 
Network:   Device-1: Qualcomm Atheros Killer E2400 Gigabit Ethernet driver: alx v: kernel port: d000 bus ID: 3b:00.0 
           chip ID: 1969:e0a1 
           IF: enp59s0 state: down mac: <filter> 
           Device-2: Qualcomm Atheros QCA6174 802.11ac Wireless Network Adapter vendor: Bigfoot Networks driver: ath10k_pci 
           v: kernel port: d000 bus ID: 3c:00.0 chip ID: 168c:003e 
           IF: wlp60s0 state: up mac: <filter> 
           Device-3: Qualcomm Atheros type: USB driver: btusb bus ID: 1-5:4 chip ID: 0cf3:e300 
Drives:    Local Storage: total: 1.02 TiB used: 730.08 GiB (70.0%) 
           ID-1: /dev/sda vendor: Kingston model: SM2280S3G2120G size: 111.79 GiB speed: 6.0 Gb/s serial: <filter> 
           ID-2: /dev/sdb vendor: HGST (Hitachi) model: HTS721010A9E630 size: 931.51 GiB speed: 6.0 Gb/s serial: <filter> 
RAID:      Hardware-1: Intel 82801 Mobile SATA Controller [RAID mode] driver: ahci v: 3.0 bus ID: 00:17.0 chip ID: 8086.282a 
Partition: ID-1: / size: 38.32 GiB used: 30.85 GiB (80.5%) fs: ext4 dev: /dev/sda4 
           ID-2: /home size: 71.26 GiB used: 57.85 GiB (81.2%) fs: ext4 dev: /dev/sda2 
Sensors:   System Temperatures: cpu: 54.5 C mobo: N/A gpu: nouveau temp: 54 C 
           Fan Speeds (RPM): N/A 
Info:      Processes: 262 Uptime: 5m Memory: 7.66 GiB used: 2.53 GiB (33.0%) Init: systemd v: 243 Compilers: gcc: 9.1.0 
           clang: 8.0.1 Shell: bash v: 5.0.11 running in: konsole inxi: 3.0.36