You can try with this study for example.
lichess.org/study/VDqRngUx/mPQaps9F
Go to "misc 10" chapter. Play a pawn move one "could" in the opening, for example a2-a4. Now SCROLL DOWN. It shows a big text box describing the opening. Even if this is a position that doesn't have openings, it's a middlegame!
It might not work for you because it's MY study. So, it maybe necessary for you to create an study chapter with a fen like this:
r3r2k/1ppbq1pp/p1pb1p2/2n5/3NPP2/1P4Q1/PBPN2PP/4RRK1 w - - 0 1
Now, play a4 or a3, or any pawn move you could in the opening, scroll down, and discover the bug.
lichess.org/study/VDqRngUx/mPQaps9F
Go to "misc 10" chapter. Play a pawn move one "could" in the opening, for example a2-a4. Now SCROLL DOWN. It shows a big text box describing the opening. Even if this is a position that doesn't have openings, it's a middlegame!
It might not work for you because it's MY study. So, it maybe necessary for you to create an study chapter with a fen like this:
r3r2k/1ppbq1pp/p1pb1p2/2n5/3NPP2/1P4Q1/PBPN2PP/4RRK1 w - - 0 1
Now, play a4 or a3, or any pawn move you could in the opening, scroll down, and discover the bug.