As you might now, many kanji have undergone changes over history. Some of these changes happened while kanji were still restricted to ancient China. Others are thanks to relatively recent efforts to keep commonly used kanji on the simpler side of things.
Sometimes, these changes were minimal. Swapping in a similar looking shape with one or two fewer strokes, or merging shapes together a bit. Sometimes elements were just dropped and unique parts left behind.
Other times, they barely left anything standing. Or they just said “to hell with it” and put in something that just happens to share the same onyomi, but isn’t visually similar at all.
I can’t guarantee that these are the most drastic simplifications out there, but they’re pretty darn drastic.
Well, see if you can guess which kanji these old forms turned into. (good luck)
From my experience in Japan I would say 门 for 門 and キ for 義 are extremely common. 门 is ridiculously omnipresent. People don’t write 門 outside of formal settings, really.
㐧 you do see now and then (saw it today at a shop’s name, btw), and I have seen a couple of Japanese people using the crazy abreviation for 前 that looks like お, although I surely wouldn’t call it “common”.
The rest I’ve never encountered in the wild. Unless we are counting Showa-themed Izakayas too. But in that case a lot of weird stuff starts showing up, so I don’t really recommend it.