This is a workaround using an obsolete USB accessory that is no longer manufactured. Based on the OP's previous posts I'm guessing the computer hardware and OS are likely obsolete too.

As mentioned previously this is a USB 2.0 device, which is much slower than gigabit Ethernet. Ethernet traffic through it will be limited to USB 2.0 capabilities, as noted on Belkin's webpage for the device.

The OP's thread title was spot on though: Today's gigabit Ethernet is cheap and portable. Gigabit Ethernet over CAT 5/5e/6 copper first showed up around 1999 and has been affordable and common in consumer devices since 2010. I'm surprised that he appears to be reporting it here as a recent discovery on his part.

I don't buy the bit about needing to lug around an obsolete laptop in case something happens to it, or that a lot of other people are doing this too. A brand new well equipped modern laptop can be had nowadays for around $500... about the same price as some smartphones or tablets.