How long is reasonable to support browsers or devices that can’t even do HTTPS? HTTPS started with Netscape in 1994, 26 years ago?
The oldest "safe" version is TLS 1.2, which only gained browser support late 2013, so 7 years ago.
The article recommends not using the older unsafe versions for the sake of older browsers.
Once a feature has been out on all major browsers for a year than its fair game to use. Its also not wasting your time trying to develop a modern web app which has support for netscape navigator.
Going off the usage stats of the site I work on, almost everyone is on the latest version of their browser and the ones that are not always end up upgrading after a warning notice is sent out about old borwsers.
Also you're going to need one hell of an adaptor to connect Ethernet from 1980 to modern Ethernet. The bit protocol is the same, but the hardware is radically different. I have never used the original Ethernet, but I have personally built 10base2 networks (still have terminators in various bit boxes) and I've seen some setups with 10base5 which is the earliest Ethernet that was actually commercially deployed:
There's actual quite a number of them (like [0]) around. They can be large, but considering you can go from parallel to modern ethernet _and_ you have a choice of adapter, it's not really as big a problem as you might be foreseeing.
That's a Plipbox. One side of it speaks 10baseT (or maybe 100baseT, it doesn't really matter) and the other is a literal Centronics-style parallel port, not Ethernet at all.
The idea is, your Amiga can do PLIP (IP over the Parallel port) and this box turns that into Ethernet traffic which you can drop into any network with IP.
But if you've got some 10base5 or earlier Ethernet, this does not help you at all.
...what am I missing? Cable and DSL modems have ethernet ports don't they? Ethernet ports still support 10Mb/s and hall-duplex right? You might need a transceiver to physically adapt the connection, but its still ethernet... well, unless we're talking about pre-802.3 ethernet of which I'm not sure how compatible the frames are.