I have an app for offline transaction generation (https://github.com/aafomin/gerbera) and it literally took me one day to implement sending to P2SH and spending from P2SH-P2WPKH (one-signture segwit).

The spec is quite straightforward and even links to an example to check your implementation.

One damn day to read the docs and implement it. You may check it yourself – it works for testnet too so that you do not risk your real Bitcoin.

Like hell I will believe now that major participants have problems implementing it. They just don't want to.