Another day another door.
Video
https://www.reddit.com/r/Minecraft/comments/fir443/double_door_fast_seamless_compact_tutorial/

I think this is the final design of these doors I'm doing.
but I had to do more testing with that neat seamless design, and I think for this it's about as same as it could be.
I did it in 1.16 too cuz target blocks can redirect redstone too and don't need a block under them and it makes it a littler cheaper.
but who know they might change something with the redstone yet in 1.16 and it not work anymore so just this one.

Edit: you can use glazed terracotta instead of hoppers, and you can remove the normal piston and use a normal block and drop the redstone down, the hoppers i needed for the 1.16 because the pistons were 1 block higher.