Os eventos do Enterprise são considerados canônicos?

There's no particular reason to believe Empreendimento is non-canon. It was created by Rick Berman and Brannon Braga, who were at one time showrunners of The Next Generation, Espaço Profundo Novee Viajante.

In-universe, we can connect Empreendimento to almost every other definitely-canon Jornada nas Estrelas propriedade:

• PARA% S: The fourth-season Empreendimento two-parter "In a Mirror, Darkly" is a sequel story to the TOS season 3 episode "The Tholian Web", and a prequel to the season 2 episode "Espelho Espelho".

• TNG: No Empreendimento series finale, "These are the Voyages...", Commander Riker is interacting with a holodeck recreation of the Empreendimento crew in order to help him sort out an internal conflict, part of the seventh season TNG episode "The Pegasus".

• DS9: Aside from the fact that being connected to TNG automatically connected Empreendimento to DS9, the Empreendimento episódio "Acquisition" introduces us to the Ferengi well before their official first contact in TNG. In the episode, a Ferengi named Krem is educating Captain Archer on the Rules of Acquisition:

  Krem: Never allow family to stand in the way of profit.

  Archer: Another of your rules?

  Krem: Number six.

  ^{Enterprise Season 1 Episode 19 "Acquisition"}

  Enquanto isso, em "The Nagus", Quark quotes the Sixth Rule of Acquisition as:

  Quark: Never allow family to stand in the way of opportunity.

  ^{Deep Space Nine Season 1 Episode 11 "The Nagus"}

• Primeiro Contato In addition to James Cromwell reprising his role as Zefram Cochrane (in a cameo), and a blink-and-you'll-miss-it glimpse of the Phoenix (Ver a Na escuridão entry, below), the events of Primeiro Contato are referenced by Captain Archer, remembering a speech made by a very drunk Cochrane:

  Archer: When I was a kid, I read everything I could about him. It took me a while, but I finally found it in the database. He was giving a commencement address at Princeton when he started to talk about what really happened during First Contact. He mentioned a group of cybernetic creatures from the future who tried to stop his first warp flight when he was living in Montana. He said they were defeated by a group of humans who were also from the future.

  ^{Star Trek Enterprise Season 2 Episode 23: "Regeneration"}

• Jornada nas Estrelas (2009): When Spock and Kirk first encounter Scotty on Delta Vega, Scotty tells us how he came to be stuck with his less-than-enviable assignment:

  Scotty: Had a little debate with my instructor on relativistic physics and how it pertains to subspace travel. He seemed to think the range of transporting something like a...like a grapefruit was limited to about a hundred miles. I told him that I could not only beam a grapefruit from one planet to the adjacent planet in the same system - which is easy, by the way - I could do it with a lifeform. So, I tested it out on Admiral Archer's prized beagle.

  ^{Star Trek (2009)}

  Emphasis mine. As discussed in another question¹, this is Admiral Sam Beckett Jonathan Archer, and Porthos from Empreendimento

• Star Trek - Além da Escuridão: Almirante Robocop Marcus has a bunch of model air and space vehicles, from the Folheto Wright all the way to his own USS Vengeance:

  

  I took this screenshot myself, so apologies for the blurriness.

  On the far right is clearly the Phoenix, Zefram Cochrane's warp-capable missle, from the movie Primeiro Contato e a Empreendimento title sequence. It's hard to make out, but I believe the middle one is the NX-Alpha, the Warp-2 prototype that appears in the Empreendimento episode "First Flight" (Season 2, Episode 24). The one on the far left is clearly the NX-01 herself.

  QMx, the company that made the models, confirms my suspicions on their website. They have a gallery of the 14 miniatures they made for the movie, one of which is the NX-01. Although it looks slightly different from the show (the two-tone hull plating, for instance) it's unquestionably the same design.

  Here's a thumb of the NX-Alpha model:

  

  And a high-res of the NX-01 model:

  

• Star Trek Beyond: Captain Balthazar Edison is described as having been a MACO before the Federation was founded (and the MACOs disbanded). He later reveals that he fought in the Xindi campaign:

  Edison: I fought for Humanity! Lost millions to the Xindi and Romulan wars.

  ^{Star Trek Beyond (2016)}

  Both the MACOs and the Xindi campaign were fixtures of Empreendimento's third season.

• descoberta: Among a handful of background references, vários mid-season episodes of descoberta make a plot point of the USS Desafiador's presence in the Mirror Universe, something that was initially established during the Empreendimento two-parter "In a Mirror, Darkly."

  As well, in her speech to the descoberta's crew at the end of "The War Without, The War Within", Admiral Cornwall references Archer's visit to Qo'noS from the Empreendimento series premiere.

Although the show wasn't as broadly well-received by Trek fans as some of the others, as far as I know no significant portions of the fanbase have rejected it, and it's never been officially rejected by Paramount, as TAS once was². Na verdade, o NX-01 Empreendimento is listed on the database at StarTrek.com, as close to an official canon repository as I can find.

The only reason I can think of to exclude Empreendimento from canon is if you're only considering things made with Gene Rodenberry's direct involvement. If that's you, then disregard the above.

¹ Disclaimer: I have the top-voted, accepted answer on this question

² Although this decision has since been reversed. TAS episodes are listed in the same database on StarTrek.com

AFAIK all of the television shows are the primary canon, (maybe not the cartoon). This was not a spin off series; it was the next official Star Trek series after Viajante.

If "canonical" means TOS, TNG, DS9, Voyager, and all of the films up to and including Nêmesis (but not necessarily J.J. Abrams' attempt at "Star Trek"), then the answer is Sim, Empreendimento is canon.

The proof that the television series Empreendimento is tethered to, and intended to be part of, the same continuity as the shows and films above is the final episode of Empreendimento, titled "These Are the Voyages". In that episode, it is revealed that the events of Empreendimento are historical events known to the characters of TNG. Specifically, Riker uses events that occurred on Captain Jonathan Archer's Enterprise as a guide as to how to proceed in a difficult decision related to the TNG episódio "O Pegasus".

The answer is "sorta"...

Before the start of Enterprise Temporal Forces are known to be interfering changing the timeline in various ways such as the Xindi War so that the events of many episodes play out Similar but not completely canon with the rest of the universe until after season 3's (i think) reset of the timeline which erased all or a significant amount of the changes from the history and returns the Enterprise crew with their non-canon memories to the canon timeline...

So canonically the Xindi War did not happen to the universe, but did happen to the Crew which does affect the overall future actions past that point... which are all supposedly canon meaning that the events that were changed were always meant to be changed and changed back or something like that.

That's if you are asking if the events are "canon" within the universe. If you mean, is the show canon with regards to how it is to be regarded as having happened or not in general the IP's canon, then yes. It is definitely canon.

I believe Enterprise to be canon, I believe everything is or should be canon. As far as I can tell, very little contradicts severely. Anyway, I think that most, not all, of the nx-01's missions/adventures were classified or not known in-universe. That said, I wish we saw Q. Anything is possible. Even though they tried to connect Enterprise with the rest, and there was time travel, we never saw the future we know. Except Riker.