No sound 27" 5K 2017 imac

i have a 2017 27" imac with no sound from either internal speakers or from the headphone socket

here is the output of inxi -Fza

System:    Kernel: 5.8.6-1-MANJARO x86_64 bits: 64 compiler: N/A 
           parameters: BOOT_IMAGE=/boot/vmlinuz-5.8-x86_64 root=UUID=e0489322-5798-491d-86b0-28cf73468f77 rw quiet apparmor=1 
           security=apparmor udev.log_priority=3 
           Desktop: KDE Plasma 5.19.5 tk: Qt 5.15.0 wm: kwin_x11 dm: SDDM Distro: Manjaro Linux 
Machine:   Type: Laptop System: Apple product: iMac18,3 v: 1.0 serial: <filter> Chassis: type: 9 v: Mac-BE088AF8C5EB4FA2 
           serial: <filter> 
           Mobo: Apple model: Mac-BE088AF8C5EB4FA2 v: iMac18,3 serial: <filter> UEFI: Apple v: 428. date: 06/16/2020 
CPU:       Topology: Quad Core model: Intel Core i5-7600 bits: 64 type: MCP arch: Kaby Lake family: 6 model-id: 9E (158) 
           stepping: 9 microcode: D6 L2 cache: 6144 KiB 
           flags: avx avx2 lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx bogomips: 28009 
           Speed: 800 MHz min/max: 800/4100 MHz Core speeds (MHz): 1: 800 2: 800 3: 800 4: 800 
           Vulnerabilities: Type: itlb_multihit status: KVM: VMX disabled 
           Type: l1tf mitigation: PTE Inversion; VMX: conditional cache flushes, SMT disabled 
           Type: mds mitigation: Clear CPU buffers; SMT disabled 
           Type: meltdown mitigation: PTI 
           Type: spec_store_bypass mitigation: Speculative Store Bypass disabled via prctl and seccomp 
           Type: spectre_v1 mitigation: usercopy/swapgs barriers and __user pointer sanitization 
           Type: spectre_v2 mitigation: Full generic retpoline, IBPB: conditional, IBRS_FW, STIBP: disabled, RSB filling 
           Type: srbds mitigation: Microcode 
           Type: tsx_async_abort mitigation: Clear CPU buffers; SMT disabled 
Graphics:  Device-1: Advanced Micro Devices [AMD/ATI] Ellesmere [Radeon RX 470/480/570/570X/580/580X/590] vendor: Apple 
           driver: amdgpu v: kernel bus ID: 01:00.0 chip ID: 1002:67df 
           Device-2: Apple FaceTime HD Camera (Built-in) type: USB driver: uvcvideo bus ID: 1-5:3 chip ID: 05ac:8511 
           serial: <filter> 
           Display: x11 server: X. Org 1.20.8 compositor: kwin_x11 driver: amdgpu FAILED: ati unloaded: modesetting 
           alternate: fbdev,vesa display ID: :0 screens: 1 
           Screen-1: 0 s-res: 2560x1440 s-dpi: 96 s-size: 676x380mm (26.6x15.0") s-diag: 775mm (30.5") 
           Monitor-1: eDP res: 2560x1440 hz: 60 dpi: 109 size: 597x336mm (23.5x13.2") diag: 685mm (27") 
           OpenGL: renderer: AMD Radeon RX 480 Graphics (POLARIS10 DRM 3.38.0 5.8.6-1-MANJARO LLVM 10.0.1) v: 4.6 Mesa 20.1.7 
           direct render: Yes 
Audio:     Device-1: Intel 100 Series/C230 Series Family HD Audio driver: snd_hda_intel v: kernel bus ID: 00:1f.3 
           chip ID: 8086:a170 
           Device-2: AMD Ellesmere HDMI Audio [Radeon RX 470/480 / 570/580/590] driver: snd_hda_intel v: kernel 
           bus ID: 01:00.1 chip ID: 1002:aaf0 
           Sound Server: ALSA v: k5.8.6-1-MANJARO 
Network:   Device-1: Broadcom and subsidiaries BCM43602 802.11ac Wireless LAN SoC vendor: Apple driver: brcmfmac v: kernel 
           port: 3000 bus ID: 03:00.0 chip ID: 14e4:43ba 
           IF: wlp3s0 state: up mac: <filter> 
           Device-2: Broadcom and subsidiaries NetXtreme BCM57766 Gigabit Ethernet PCIe driver: tg3 v: kernel port: 3000 
           bus ID: 04:00.0 chip ID: 14e4:1686 
           IF: enp4s0f0 state: down mac: <filter> 
Drives:    Local Storage: total: 1.04 TiB used: 14.77 GiB (1.4%) 
           SMART Message: Unable to run smartctl. Root privileges required. 
           ID-1: /dev/nvme0n1 vendor: Apple model: SSD SM0032L size: 26.08 GiB block size: physical: 4096 B logical: 4096 B 
           speed: 15.8 Gb/s lanes: 2 serial: <filter> rev: DXZ77A0Q scheme: GPT 
           ID-2: /dev/sda vendor: Apple model: HDD ST1000DM003 size: 931.51 GiB block size: physical: 4096 B logical: 512 B 
           speed: 6.0 Gb/s rotation: 7200 rpm serial: <filter> rev: AQ04 scheme: GPT 
           ID-3: /dev/sdb type: USB model: KESU USB 3.0 size: 111.79 GiB block size: physical: 4096 B logical: 512 B 
           serial: <filter> rev: 0209 scheme: GPT 
Partition: ID-1: / raw size: 111.49 GiB size: 109.24 GiB (97.98%) used: 14.77 GiB (13.5%) fs: ext4 dev: /dev/sdb2 
Swap:      Alert: No Swap data was found. 
Sensors:   System Temperatures: cpu: 57.0 C mobo: N/A gpu: amdgpu temp: 53 C 
           Fan Speeds (RPM): N/A 
Info:      Processes: 231 Uptime: 1m Memory: 7.67 GiB used: 802.0 MiB (10.2%) Init: systemd v: 246 Compilers: gcc: 10.2.0 
           Packages: 1243 pacman: 1237 lib: 352 flatpak: 0 snap: 6 Shell: Bash v: 5.0.18 running in: yakuake inxi: 3.1.05```

What DE are you using? Check alsamixer levels.