- Intel doesn't releases fanless NUCs.
- However there are company on the market that have on sale fanless NUCs. For example SimplyNUC: https://simplynuc.co.uk/nuc-products/
- Other possibility is to buy NUC board and AKASA case. Then you can build your fanless NUC: http://www.akasa.com.tw/update.php?tpl=product/product.list.tpl&type=Fanless%20Chassis&type_sub=Fanl...
While not made anymore, the Intel® NUC Kit DE3815TYKHE was a fanless unit if I am not mistaken -> https://www.intel.com/content/www/us/en/support/products/78577/mini-pcs/intel-nuc-kits/intel-nuc-kit... Technical specs here -> https://www.intel.com/content/dam/support/us/en/documents/mini-pcs/nuc-kits/DE3815TYBE_TechProdSpec....
Chaco Canyon supports add-on adapters and this can be used to add features such as this. GO-RITE has built a number of these adapters (which can be found here: https://www.microsatacables.com/intel-nuc-products/chaco-canyon or here: https://www.gorite.com/intel-nuc-products/chaco-canyon). Now, there doesn't seem to be one that foots the bill just yet. Perhaps you should contact GO-RITE and discuss this with them...
The following NUC families have a mini-Toslink jack at the back panel that outputs multi-channel digital audio:
Akasa makes fanless Newton cases for these 3 series of NUCs, and I have one each of NUC7PJYH, NUC6CAYS and NUC5PPYH running fanless and headless in their respective Akasa Newton cases, for purposes including NAA (network audio adapter).