The only real way to know is making a test install on a spare USB key and then (if there's an issue) share the boot log and "lsusb" output so we can check the PCI card IDs against upstream kernel drivers. Most PCI audio cards use generic drivers and should just work. Occasionally we need to enable the driver in kernel config. Occasionally we need to patch a new card ID.
How about Asus Xonar series? Will it works?
usually the way to figure this should be a google search string "linux Asus Xonar" or better "linux <correct device vendor naming here >"
but be aware: vendor sometimes changes chips/etc. and sell the stuff with the same product name.
so you should check how current it is what google have found
as chewitt said:
I would buy one with warranted(!) exchange (and for the worst case: money back) and test with a usb stick
https://www.asus.com/de/Motherboards-Components/Sound-Cards/Hi-Fi/Xonar_U5/
its usb and works like a charm 
I had a xonar dx2 using the coax out didn't like it, too much faffing around. what receiver are you using? Can't you go direct from hdmi to it? If you have a none 4k receiver but want to use 4k video while separating the audio to coax there are a few other options.
I had a xonar dx2 using the coax out didn't like it, too much faffing around. what receiver are you using? Can't you go direct from hdmi to it? If you have a none 4k receiver but want to use 4k video while separating the audio to coax there are a few other options
my old receiver have only spdif, philips fr975, it's very budget setup =)
I used an extractor from my xbox x to my anthem mrx500, took the hdmi and sent video back to hdmi and audio out to optical. has some dip switches as well to help with extraction. cheaper than a sound card
Sometime earlier this year I tried the following ASUS Xonar cards with C-Media CMI8788 chips (a.k.a Oxygen HD) under LE10, both analog and S/PDIF outputs worked (including passthrough):
However, I also read about these cards that they actually cause sound quality problems with newer generation PCs. But my old i7-3770 had no such problem.
