How to select tls v1.2 when use the built-in TLS library

[ryanchang419]

My goal is to build a websocket client that needs two-way authentication to connect to the server.
Now I am evaluating the feasibility, so I tested it on ubuntu24. The mongoose repository version I pulled is 7.17.
First I used openssl, and when I used openssl, the program worked fine.
But when I switched to the built-in TLS library, some errors occurred: error code 40

I used tcpdump to capture the packet and checked it in wireshark, and found the following information

In the extension content, I can see that there is only TLS 1.3. Does this mean that the built-in library of this version no longer supports v1.2 (I guess not)? If not, how can I enable support for v1.2?

I am using translation software. If there is anything unclear in the description, please let me know and I will provide more clear instructions.
Thank you very much!

[scaprile]

Our TLS is TLS1.3. It is not 1.2, it is 1.3. There is no "no longer", it has been 1.3 right from the start

[ryanchang419]

Thanks for your answer! I guess I can only solve this problem from the server side.

[scaprile]

You can uprade your server
You can use MbedTLS, OpenSSL, WolfSSL
Both MbedTLS and WolfSSL can work in embedded environments, though yes, our stack is quite smaller