[ipq806x] How to determine the presence of a link on each LAN port?

OpenWRT v23 will most likely get the updated package luci-mod-status.
PR: https://github.com/openwrt/luci/pull/5918

And now each physical port will be visually displayed to the user.

But on the ipq806x platform, one ETH interface is responsible for all physical LAN ports.

Is it possible to get detailed information on each physical LAN port?

Not using luci-mod-status in its current form, someone (read, probably you) would have to develop equivalent support for swconfig based devices (and keep in mind, DSA for ipq806x is on the table, while not merged yet, it's functional and just waiting to be merged, while that won't help you for 23.05.x, it does limit the motivation developers might want to spend on swconfig).