Which LE version are you using?
I did a quick test on LE12 nightly and oddly kodi showed it under the name of my soundcard but with empty parenthesis after them (usually they have he name of the soundcard, again). Certainly some kodi oddity but I saw it in the log, too:
2023-09-25 18:58:05.085 T:1120 info <general>: Device 3
2023-09-25 18:58:05.085 T:1120 info <general>: m_deviceName : both
2023-09-25 18:58:05.085 T:1120 info <general>: m_displayName : RPi-Cirrus ()
2023-09-25 18:58:05.085 T:1120 info <general>: m_displayNameExtra: WM5102 AiFi wm5102-aif1-0
2023-09-25 18:58:05.085 T:1120 info <general>: m_deviceType : AE_DEVTYPE_PCM
2023-09-25 18:58:05.085 T:1120 info <general>: m_channels : FL, FR, BL, BR, FC, LFE, SL, SR, UNKNOWN1, UNKNOWN2, UNKNOWN3, UNKNOWN4, UNKNOWN5, UNKNOWN6, UNKNOWN7, UNKNOWN8
2023-09-25 18:58:05.085 T:1120 info <general>: m_sampleRates : 32000,44100,48000
2023-09-25 18:58:05.085 T:1120 info <general>: m_dataFormats : AE_FMT_S24NE4,AE_FMT_S32NE,AE_FMT_S16NE,AE_FMT_S16LE
2023-09-25 18:58:05.085 T:1120 info <general>: m_streamTypes : No passthrough capabilities
If you can't get it working please provide a debug log (enabled debug logging in settings, reboot, ssh in and run "pastekodi").
If you play multichannel content and have the number of channels set to 2 in kodi audio config then kodi will downmix to 2ch automatically.
OFC you could also configure more channels, like you did before (also increase the number of channels in the multi pcm accordingly) and eg map 6 channels to HDMI and only FL and FR to the soundcard - but then you'll loose the center channel at the soundcard when playing 5.1 contents.
You could play around with ttable and down-mix more channels into left and right of the soundcard but that could have negative effects if you only output stereo content.
It's tricky, you have to play around a bit what you prefer.
so long,
Hias