Which TCP/IP chip on new design?

I’m designing a board where I want to add ethernet connectivity to open a TCP connection to a server.
There may be 2 TCP connections active at the same time.
1 as a client and 1 as a listener (server).

The data layer will be just telemetry information. There is no need for high speed communications.

I think W6100 is a good choice but I’m worried about the availability in the long term.
The only chip that W6100 is compatible is the W5100S.
On the other hand there’s W5500 and I find plenty of stock in the market. However it is not drop-in compatible with any other options.
Also, W5500 seems to not be compatible with W6100 with the software.

Is W5500 software-registers compatible with W6100 for my application?
How about W5100S?
What is the future availability of W6100?