You might still have an old Apple Ethernet USB adapter lying around that you would like to continue using under macOS 10.14, 10.15 or even macOS 11 Big Sur? All you need is a driver.
The adapter offers only 100 Mbit/s speed, but to connect a Mac to the internet it is still sufficient. And why throw it away when it only needs new software? Apple has simply omitted the corresponding drivers in new operating system versions. We simply install again.
100 Mbit/s Apple Ethernet Adapter A1277 under macOS 11 Big Sur
Since Apple of course also does not manufacture the adapter itself, it is easy to find out that the model internally called A1277 comes from ASIX Electronics, where it goes by the name AX88772C. On the manufacturer’s page, we simply search for the corresponding model and lo and behold: there are a lot of drivers available!
Driver for 100 Mbit/s adapter from Apple for macOS 10.14, 10.15, 11
Namely, the detailed driver page offers not only drivers for macOS 10.9 to 10.15, but also a beta version for macOS 11 (for hobbyists for now). But also for Windows and Linux you have the free choice! So you can continue to use the old adapter until its demise.