When browsing sites that use SELECT dropdowns, the dropdown box cannot be interacted with using the mouse. Using the keyboard to select a select box, then using the up / down arrow to change options works - but you cannot select / change the contents of the select box via the mouse. This works fine if you start firefox with: GDK_BACKEND=x11 firefox GPU is an AMD RX5700XT. An example web site is: https://www.ebay.com.au/itm/USB-Type-A-to-Mini-USB-90-Angle-Male-Plug-Adapter-Cable-M-M-Cord-Left-Right-AM/163915670633 $ rpm -qa | grep firefox firefox-70.0.1-4.fc31.x86_64 $ rpm -qa | grep mesa | sort mesa-dri-drivers-19.2.4-1.fc31.i686 mesa-dri-drivers-19.2.4-1.fc31.x86_64 mesa-filesystem-19.2.4-1.fc31.i686 mesa-filesystem-19.2.4-1.fc31.x86_64 mesa-libEGL-19.2.4-1.fc31.x86_64 mesa-libgbm-19.2.4-1.fc31.x86_64 mesa-libGL-19.2.4-1.fc31.i686 mesa-libGL-19.2.4-1.fc31.x86_64 mesa-libglapi-19.2.4-1.fc31.i686 mesa-libglapi-19.2.4-1.fc31.x86_64 mesa-libGLU-9.0.1-1.fc31.x86_64 mesa-libxatracker-19.2.4-1.fc31.x86_64 mesa-vdpau-drivers-19.2.4-1.fc31.x86_64 mesa-vulkan-drivers-19.2.4-1.fc31.i686 mesa-vulkan-drivers-19.2.4-1.fc31.x86_64 $ rpm -qa | grep llvm | sort llvm-libs-9.0.0-1.fc31.i686 llvm-libs-9.0.0-1.fc31.x86_64 $ lspci | grep VGA 1e:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Navi 10 [Radeon RX 5700 / 5700 XT] (rev c1) $ dmesg | grep -i amdgpu [ 3.952520] [drm] amdgpu kernel modesetting enabled. [ 3.952647] amdgpu 0000:1e:00.0: remove_conflicting_pci_framebuffers: bar 0: 0xe0000000 -> 0xefffffff [ 3.952648] amdgpu 0000:1e:00.0: remove_conflicting_pci_framebuffers: bar 2: 0xf0000000 -> 0xf01fffff [ 3.952649] amdgpu 0000:1e:00.0: remove_conflicting_pci_framebuffers: bar 5: 0xfca00000 -> 0xfca7ffff [ 3.952651] fb0: switching to amdgpudrmfb from EFI VGA [ 3.952684] amdgpu 0000:1e:00.0: vgaarb: deactivate vga console [ 3.972884] amdgpu 0000:1e:00.0: No more image in the PCI ROM [ 3.972930] amdgpu 0000:1e:00.0: VRAM: 8176M 0x0000008000000000 - 0x00000081FEFFFFFF (8176M used) [ 3.972931] amdgpu 0000:1e:00.0: GART: 512M 0x0000000000000000 - 0x000000001FFFFFFF [ 3.973032] [drm] amdgpu: 8176M of VRAM memory ready [ 3.973034] [drm] amdgpu: 8176M of GTT memory ready. [ 4.588976] amdgpu: [powerplay] SMU is initialized successfully! [ 4.825139] fbcon: amdgpudrmfb (fb0) is primary device [ 4.825141] amdgpu 0000:1e:00.0: fb0: amdgpudrmfb frame buffer device [ 4.833050] amdgpu 0000:1e:00.0: ring 0(gfx_0.0.0) uses VM inv eng 4 on hub 0 [ 4.833051] amdgpu 0000:1e:00.0: ring 1(gfx_0.1.0) uses VM inv eng 5 on hub 0 [ 4.833052] amdgpu 0000:1e:00.0: ring 2(comp_1.0.0) uses VM inv eng 6 on hub 0 [ 4.833052] amdgpu 0000:1e:00.0: ring 3(comp_1.1.0) uses VM inv eng 7 on hub 0 [ 4.833053] amdgpu 0000:1e:00.0: ring 4(comp_1.2.0) uses VM inv eng 8 on hub 0 [ 4.833054] amdgpu 0000:1e:00.0: ring 5(comp_1.3.0) uses VM inv eng 9 on hub 0 [ 4.833054] amdgpu 0000:1e:00.0: ring 6(comp_1.0.1) uses VM inv eng 10 on hub 0 [ 4.833055] amdgpu 0000:1e:00.0: ring 7(comp_1.1.1) uses VM inv eng 11 on hub 0 [ 4.833056] amdgpu 0000:1e:00.0: ring 8(comp_1.2.1) uses VM inv eng 12 on hub 0 [ 4.833056] amdgpu 0000:1e:00.0: ring 9(comp_1.3.1) uses VM inv eng 13 on hub 0 [ 4.833057] amdgpu 0000:1e:00.0: ring 10(kiq_2.1.0) uses VM inv eng 14 on hub 0 [ 4.833057] amdgpu 0000:1e:00.0: ring 11(sdma0) uses VM inv eng 15 on hub 0 [ 4.833058] amdgpu 0000:1e:00.0: ring 12(sdma1) uses VM inv eng 16 on hub 0 [ 4.833059] amdgpu 0000:1e:00.0: ring 13(vcn_dec) uses VM inv eng 4 on hub 1 [ 4.833059] amdgpu 0000:1e:00.0: ring 14(vcn_enc0) uses VM inv eng 5 on hub 1 [ 4.833060] amdgpu 0000:1e:00.0: ring 15(vcn_enc1) uses VM inv eng 6 on hub 1 [ 4.833060] amdgpu 0000:1e:00.0: ring 16(vcn_jpeg) uses VM inv eng 7 on hub 1 [ 4.833207] [drm] Initialized amdgpu 3.33.0 20150101 for 0000:1e:00.0 on minor 0
I'm seeing the same issue here as well. firefox-70.0.1-4.fc31.x86_64 on Fedora 31, Wayland, Intel GPU (Intel Corporation HD Graphics 620 (rev 02)). It happens with or without hardware acceleration enabled in Firefox and is a recent regression.
Another workaround is to install the "firefox-x11" package and start firefox with the "firefox-x11" command. This wrapper just sets MOZ_DISABLE_WAYLAND=1, which I assume achieves something similar to GDK_BACKEND=x11 mentioned in OP.
Possibly a duplicate of https://bugzilla.redhat.com/show_bug.cgi?id=1773715 . Upstream bug appears to be https://bugzilla.mozilla.org/show_bug.cgi?id=1591936
*** This bug has been marked as a duplicate of bug 1773715 ***