You are going to have to be more detailed in your question but your question would be very similar to can I use a pcie card instead of a cable modem. I have never seen such a device.
Now maybe there is a device like that but in addition to it technically working it must be fully compatible and even more important supported by the ISP. Part of the reason cable modem and ONT have restricted lists of supported units is the ISP is responsible for all firmware updates.
This both ensure that the device is always compatible with the ISP equipment as well as provides the security. Most cable and fiber networks depend on something like a mac address on the device that must be registered otherwise if any device is allowed then you could use the system without paying for it by tapping into the line.
So even if a PCIE card exists I doubt a ISP will let you use it. On internal cards all the software is loaded via drivers loaded by the OS. You not the ISP would be in control of this software which might not say work if they needed to push a patch out on a particular day. In addition it likely would allow you to hack thing like the mac address which would bypass their security.
I suspect it not so much a technical question since a device might exist to be used on a private fiber network but more if you found such a device would the ISP even let you use it.