Do native speakers use the subjunctive mood?

I do but it’s reinforced by my dialects preference for were over was. Most don’t always use it and are easily understood.

Yeah

We do and we don't. In this case I think I'd use imperative even if it's grammatically "incorrect," but I wouldn't bat an eye if someone used the subjunctive. With that said, if someone were to say, "I wish things are different," I'd think it sounds strange. "I wish things \*were\* different" -- the subjunctive -- is really the only way to convey this phrase. Tldr it's a case-by-case basis, but the subjunctive overall isn't obsolete.

I use it occasionally, mostly when talking with coworkers. I don't use it when talking with friends or family.

Yes all the time. "We expect that the car be returned with a full tank of gas" sounds good "We expect that the car is returned with a full tank of gas" sounds much less idiomatic to me. Obviously I understand the meaning but, to my ears, it feels wrong.

another example of subjunctive being erased: fiddler on the roof 1971 "if i were a rich man", gwen stefani 2004 "if i was a rich girl".

There are a wide variety of subjunctive structures and some are more used than others. But they are, generally speaking, used. Very few people learn the word "subjunctive" before studying French or Spanish, though. It can make a difference in the perfect context, but usually it's not something people really notice.

Yes, we use it. "I suggest we take a break", "I wish I lived in London", "If I were you, I'd take the train", "Be that as it may...", "You can borrow my car if need be."

The example sentence sounds weird but this is not on account of the subjunctive. The example sentence sounds weird because, for one thing, the relative pronoun ("that") has been omitted, and, for another thing, because the main verb ("I'll") is in the future tense whereas we would expect the hypothetical present ("I'd"). "I'd recommend that Sam join your party" sounds perfectly fine.

Yes, but usually only in formal contexts. You'll hardly ever hear it used in casual conversation. It feels a bit stiff/overly formal.

I think it's funny how in the real world if you ask a native speaker about the subjunctive mood they'd have absolutely no idea what you're talking about. One of those surprisingly refreshing observations.

Abusing the heck out of subjunctives can make you look all wishy washy. Remember that if you have to use a subjunctive, it is mostly because somewhere deep in your mind, you wished for it to happen.

Yes, we do.

Oh definitely. Not everyone knows the term (or remembers it) but probably everyone uses it. 

Yes, especially in more formal contexts.

It is used interchangeably with the indicative. Both 'join' and 'joins' would be natural and normal in your example.

Yes, a lot of people use it. I would have used "that" in that sentence. It sounds weird to me without it. "I'll recommend that Sam join the party"

Yes we use it. It can sound a bit formal in some situations, and casual conversation often just uses the indicative instead, but it’s definitely in common use.

We use it and we don't. Technically the subjunctive is correct, but you will hear both used interchangeably in general conversation. Most native speakers probably won't even be able to tell you the difference. I'm fuzzy on it myself. It is important that he is at the meeting. It is important that he be at the meeting. The second one is the subjunctive, and is correct, but most people will probably use the first in day to day talk.

It's my natural grammar to use it where appropriate. When I speak with someone who comes from an area where it's dying out, it tends to grate on my ear when they skip it. You're going to find that this is a regional issue, and also a generational one. I, in my mid sixties, use it, but youngsters from my same area often do not.

It’s imperative the cylinder remains unharmed.

I'd say "I'll recommend *that* Sam join the party", but I think that's bc I'm American and we rly like our relative clause markers. But yeah people use the subjunctive

Speakers of British English commonly eschew the subjunctive, and use the indicative instead. On the other hand, speakers of American English use the subjunctive in everyday conversation. The result is that to an American ear, sentences that are common and ordinary in British English sound strange, illiterate, and ignorant to speakers of American English. For example, in a description of the plans for the coronation of King Charles and Queen Camilla, in describing the queen's crown the British newspaper *Daily Mail* wrote "Camilla has also requested that four of the eight detachable arches **are** removed." This sentence sounds completely wrong to most American speakers of English; for us, we would expect "Camilla has also requested that four of the eight detachable arches ***be*** removed."

We use it all the time, and we don’t even notice.

English does not have a verb form specifically to mark the subjunctive. It is generally covered by a topic like indicative and non-indicative moods, the latter being divided into four categories of which one is the subjunctive. So native speakers will indeed use what is referred to as the subjunctive in other languages, but they might just know it as one of the non indicative moods, and typically think that it seems exactly the same as the other three in terms of verb form so conclude that the distinctions don't seem to matter much.

That particular construction is considered archaic in the UK. It’s still standard written English in the U.S., although in my experience talking to younger people, it seems to be losing ground at least in speech. I (40M/Inland North US) never had any trouble with it growing up.