How can we connect this printer to other computer remotely

Given the age of the Kyocera Mita hardware, parts are probably NLA (new from Kyocera). You run into this problem with the bulletproof HPs (like the LJ 4 and 5) and the HP LJ 4000 series due to their reputation for being nearly unkillable. Even the P4015 is as bulletproof as the 4000/4050/4100/4150/4200/4250b was, as it's basically the same engine with a newer toner. The solution with those is to have the card installed in the printer but keep a spare EIO card or two around as HP no longer makes them.

However, this works better with HP because of how many of them are sold, so there's a surplus of printers and accessories like cards. This isn't the case with the Kyocera you have.

The reason for the surplus of parts and printers is that the 4000 series lasers just run all day long with third-party toner installed. When configured to run on a toner low/empty condition, they will run until the toner is needed and beyond. This is why (as hard as HP has tried and failed to get these "bulletproof" machines out of circulation) they continue to have a following.... Especially with the HP DS (2016+) generation.

As @jayeff pointed out, the OEM P/N for the Ethernet card is FS-21E. I looked on eBay since that’s the key place we get the HP EIO cards, and I didn’t find any, but your best bet is to keep looking and buy one as soon as it comes up.

You're more likely to have better luck making a "print server" out of an old Windows or Mac PC, like a surplus USFF PC with an 8th/9th gen Intel process or similar Ryzen 5. You can also see if you can find a USB print server.

BEWARE: None of the 3rd party servers properly communicate the printer's model (just an IP address), so you need to install the printer manually or use generic PS/PCL drivers if there's no current driver for it. This is not an issue with first-party parts like the Kyocera or HP JetDirect cards. As such, the third-party stuff requires manual TCP/IP setup and manual driver selection.

Footnote 1: When I say bulletproof, I mean ones you can replace the plastic swing gear with a metal Printer Techs one at 250k if you need it and the ones which never had the issue like the 4000/4050 and the P4015 with benefits from the unkillable nature of the 4000 series. This annoys HP for obvious reasons to the point they tried to kill them by discontinuing the X toner cart for some of them.