I have been using a portcullis gate that uses sand to open 3 blocks high and then return flush to walk through, as shown in the YouTube video by The Bow Tie Man, it has worked perfectly since November 2019 when I build them on my realm, worked perfectly till I upgraded to 1.16 now the gravity blocks break every time it's used. I looked through the patch notes and read about the gravity and pistons being made to not break, at least that's how I read it yet they break now when they didn't used to.