There have been some news pieces put out, but most importantly

... the Physicians Committee (PCRM) said records it obtained for the 23 monkeys used in the experiments reflect a “pattern of extreme suffering and staff negligence.” The committee said that the letter to the USDA is based on nearly 600 pages of what it calls “disturbing” documents released after the committee filed an initial public records lawsuit in 2021.

Now, CNN did link to Nueralink's site, but not to PCRM. That, to me, says a lot about who you they're supporting.

If you want to read PCRMs report, it's here. Because reading the sources is always a good idea.

https://www.pcrm.org/ethical-science/animals-in-medical-research/pcrm-response-neuralink-claims

From the article posted in anothers comment:

Animal 11”: They were killed in a terminal procedure at UC Davis on March 15, 2019. Prior to this procedure, the monkey had a cranial implant surgically placed inside their brain on Dec. 3, 2018. Following this procedure, the implant became chronically infected. The monkey began to have a depressed appetite.

October 2018, UC Davis staff noted that the monkey was “missing multiple digits [on] both hands, [right] foot,” possibly from self-mutilation or some other unspecified trauma.

On Dec. 18, 2018, staff decided to “prophylactically or conservatively start [antibiotic treatment]” for the monkey after observing that “the skin was eroded” surrounding the implant. In the following two months, there are frequent observations of the monkey having a bloody, infected head wound from the device experimenters attached to their skull. The monkey was prescribed several types of antibiotics during this period. In January 2019, staff observed that the monkey had a “bloody head…dried blood around base at cranial implant.”

https://www.reuters.com/technology/musks-neuralink-faces-federal-probe-employee-backlash-over-animal-tests-2022-12-05/

A couple of excerpts here:

The first complaints about the company’s testing involved its initial partnership with University of California, Davis, to conduct the experiments. In February, an animal rights group, the Physicians Committee for Responsible Medicine, filed a complaint with the USDA accusing the Neuralink-UC Davis project of botching surgeries that killed monkeys and publicly released its findings. The group alleged that surgeons used the wrong surgical glue twice, which led to two monkeys suffering and ultimately dying, while other monkeys had different complications from the implants.

A note about Musk's use of propaganda in the face of truth (emphasis mine):

Neuralink executives have said publicly that the company tests animals only when it has exhausted other research options, but documents and company messages suggest otherwise. During a Nov. 30 presentation the company broadcast on YouTube, for example, Musk said surgeries were used at a later stage of the process to confirm that the device works rather than to test early hypotheses. “We’re extremely careful,” he said, to make sure that testing is “confirmatory, not exploratory,” using animal testing as a last resort after trying other methods.

In October, a month before Musk’s comments, Autumn Sorrells, the head of animal care, ordered employees to scrub "exploration" from study titles retroactively and stop using it in the future.

There's lots more in there and I highly recommend reading the whole article. It is from December of last year, but I'd find it hard to believe that things would have improved in the past 9 or 10 months....certainly not enough to excuse the shoddy work and unnecessary suffering caused early on in the project.