I love seeing this question because my current parish boggles my mind. I’m 34 and have grown up and attended the same archdiocese my entire life (Kansas City in KS). At my folks’ parish, the one I grew up in, we knelt through the EP, stood at the Great Amen, knelt again when the Agnus Dei was finished. Then we stood at our turn for Communion and knelt when we got back until the Tabernacle was closed.
In my 20s I attended another parish, sadly this was a time when I was away from the Church and attended sporadically, e.g. when I felt like it. My point here is that I don’t recall every single Mass but can say with certainty they followed the same process as my childhood parish. (note: it’s only 3 miles separating them and they’re both about the same age, I think.)
And now, in my 30s I attend a parish that has relatively young families and is only about 33 years old, and the sanctuary only 26 years old. Anyway, everything is as it was as a kid except…when the priest moves from the altar to the dais to distribute communion. This is the ONLY parish I have ever been to where everyone sits at this point. I, and sometimes a handful of others, continue to kneel but 98% of the congregation sits at this time until it’s their turn when they get up, come back and kneel as normal.
I’ve always found it very, very strange (and annoying/disrespectful but I’m not supposed to judge, right?) and even my Mom remarked about it the few times she’s visited our church. They also close the Tabernacle during communion (which gets under my skin - really I think it’s just a case of the EMHC not knowing
why it should remain open) but that’s another post.