PuTTY on Linux: how to copy text

Problem

I use Windows a lot) And I’m used to the fact that since 1995 there has been such a thing in the system as the clipboard, and it always works the same. Maximum, you need to do some non-standard actions so that the text gets there. For example, for the SSH PuTTY terminal client, select the text with the left mouse button.
But when using putti in Ubuntu, an unexpected problem arose: copying the text, which “here it is before my eyes”, into another application.

Decision

At least in Gnome. The desired text in the putti is highlighted with the left mouse button . In the other window you need (for example, IDE), click the middle mouse button, and the text selected in another window is inserted .

Open questions

• Why does the text not get into the real buffer from which Ctrl + V can be inserted?
• How to set it up?
• I suspect that on a mouse with only two buttons to insert it is necessary to press both of them, no?
• HOW TO DO IT WITH KEYBOARD?