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You're better off with TOSLINK instead of HDMI https://www.amazon.com/Cubilux-TOSLINK-Thunderbolt-Converter-Compatible/dp/B09QFYNB7Y FYI there's a good chance you will also need to download software to control the MacOS volume since a lot of adapters will hijack the audio and keep you locked at "full volume" I've been using SoundSource (Super Volume Keys feature) forever and I've never looked for free alternative solutions. https://rogueamoeba.com/soundsource/
You’ll need a USB adapter that has an optical SPDIF (TOSLINK) output, plus a TOSLINK cable. Connect the adapter to your computer, then run the optical cable from the adapter to your MiniDisc’s optical input. In your computer’s sound settings, select the SPDIF device as the audio output. Set your MiniDisc to record from optical, hit record, and play your audio on the computer. This a USB C to TOSLINK adapter: https://a.co/d/02TLRt3B p.s you can also use this adapter with android phones.