
James Gunn recently confirmed that two recent DC releases are not canon to the greater DCU, despite the projects featuring characters who have already appeared in the franchise. The DCU kicked off with Creature Commandos and Superman, and now fans are being treated to Peacemaker Season 2. Peacemaker changed a vital scene from Season 1 to fit within the DCU, meaning that it is 100% canon in the franchise, which is something that two other recent projects can't say for themselves.

According to DC Studios co-CEO James Gunn, the Superman prequel novel titled Superman: Welcome to Metropolis and the Krypto Saves the Day! shorts - both released with the DC Studios banner - are not canon in the DCU. The Superman tie-in novel features David Corenswet's Superman as the titular character, but the actual story that it tells never actually took place within the DCU timeline. The same goes for the shorts that feature Krypto, who was also in the Superman film.
Gunn confirmed that neither project was canon when fans specifically questioned him regarding the matter. In a response to a fan on Threads, the DC Studios chief simply stated that Superman: Welcome to Metropolis is a standalone project, saying, "It is not canon, no."
Gunn was also asked about the Krypto shorts via Threads, where he gave a similar response. In particular, Gunn said, "No. I love 'em tho," when asked if they were canon.

It is worth noting that the tie-in novel and the Krypto shorts are not the only comments Gunn has recently made about DCU canon. For example, he was also recently asked (again, via Threads) if there would ever be canon comic books that could flesh out characters outside of movies or TV shows.
In short, Gunn confirmed that there are currently no plans for canon comics to be released, largely since that could make everything in canon "hard to keep track of:"
"Even with me and our guy Phil (whose job it is to keep it all together) on canon in the DCU, with multiple films and shows it's still hard to keep track of. Adding comics at this time would be too much for the lean DC team. So right now nothing is canon outside of the filmed media."
So, according to Gunn, the only pieces of media that feature DCU characters that are considered canon will be TV shows or films. However, the Krypto Saves the Day! shorts are obviously an exception, since they are still filmed media.
Will DC Studios Release More Non-Canon Projects?
Superman was a major release for the DCU and a huge title for DC Studios and Warner Bros. in general. Superman is also one of the biggest and most popular superheroes in history, so it is not really a surprise that he received a tie-in novel.
However, fans should not expect this to happen for every DCU movie. For example, there likely will not be a tie-in Supergirl novel. If there is, then it will not be canon, but Superman was the first film in a newly established franchise, so Warner Bros. and Gunn likely thought that a tie-in novel geared toward juniors could convince some more people to come watch the movie in theaters. It may have worked, too, because Superman was reportedly a major financial success for Warner Bros.
If there is another tie-in novel or a batch of shorts released sometime relatively soon, it would likely be for the DCU's Batman film, which is still expected to be The Brave and the Bold. Batman is just as popular as Superman, so if a book or some shorts were made about the DCU's Batman, there would most definitely be some consumers for that project.