Please compile WinSCP 4.4.0 with support for new key exchange algorithms.
I tried to switch to WinSCP 5, x many times, but the tab interface turned out to be very inconvenient when working with a large number of servers. I have been using the 4.4.0 version so far. But now I cannot connect with Ubuntu 20.04 and other modern distributions for example.
I don't think I'm the only one. Already embedded on the forum a request to return the old type of server switch.