I added a couple of fixes, the new version has been uploaded to GitHub, it is available on the releases page. (9.2.6-20210209)
I tried a few previous M8 audio configurations, but none of them changed the situation, only Analog and S/PDIF options are displayed in the ALSA list.
I tried passthrough on M8S+ with basic settings, and my TV recognized Dolby AC3 correctly, but I couldn't try DTS because unfortunately it is not supported on the LG OLED TV.
Another question: What kind of S805 device do you have? Maybe an MXQ-HD18Q (a.k.a. "all black" with 1GB of RAM) or an MXQ-m201d (512MB)?
You're right it does pass through ac3 and dts, I can't select anything for pass through, only the spdif lists (which makes sense). But hence I can't select the newer ACC and DTS-HD formats. No worries, this M8S+ is from a friend and he only has an DTS capable receiver, not the newer formats.
My S805 is a M8S. About your 9.02 builds for both M8S and M8S+, they do freeze quite often. Not sure yet when, looks also stopping/starting video related. For the M8S+ the 9.2 build does a better job.