INA 212(a)(9)(B)(i) states that
Any alien (other than an alien lawfully admitted for permanent residence) who—
(I) was unlawfully present in the United States for a period of more than 180 days but less than 1 year, voluntarily departed the United States (whether or not pursuant to section 1254a(e) of this title) prior to the commencement of proceedings under section 1225(b)(1) of this title or section 1229a of this title, and again seeks admission within 3 years of the date of such alien’s departure or removal, or
(II) has been unlawfully present in the United States for one year or more, and who again seeks admission within 10 years of the date of such alien’s departure or removal from the United States,
There are two ways to interpret "other than an alien lawfully admitted for permanent residence". It could mean (1) that a lawful permanent resident who is returning to the US cannot be found inadmissible under INA 212(a)(9)(B)(i), or (2) any departure or removal from the United States while a lawful permanent resident does not trigger an INA 212(a)(9)(B)(i) bar.
(1) seems to be the most straightforward interpretation based on the plain wording of the statute. Plus, in some rare cases, it is possible for a person to obtain LPR status through a route to which 212(a)(9)(B)(i) bars, by statute, do not apply; and presumably such a person, after having obtained LPR status, has no restrictions on their ability to travel in and out of the US compared with any other LPR. It would seem bizarre and absurd to reject (1).
We can easily think of a hypothetical scenario that tests (2). A tourist entered the United States on January 1, 2016. Their period of authorized stay expired on July 1, 2016. They remained in the US unlawfully. Then, on August 1, 2017 (i.e., after more than a year of unlawful presence), they married a US citizen and applied for adjustment of status. This was granted on September 3, 2018. On December 21, 2018, they travelled outside the US for the first time since their arrival for a brief vacation, and returned to the US without incident (see (1)). Eventually, at some point in 2021, they stayed outside the US for too long, and, having abandoned their US residence, decided to submit Form I-407 to avoid any complications with returning to the US. Now, in 2022, they decide to try to move back to the US with their spouse. The US citizen spouse submits a new I-130, and the noncitizen spouse applies for an immigrant visa. What will happen? Will the consular officer notify them that due to their previous period of unlawful presence, they are inadmissible until December 21, 2028?
My hunch is that in the above scenario, the person is not considered inadmissible until December 21, 2028 because their departure from the United States after accruing more than 1 year of unlawful presence occurred while they were an LPR. In other words I think interpretation (2) is correct, but (1) is also correct: INA 212(a)(9)(B)(i) does not make LPRs inadmissible, nor is it triggered by any departure of a noncitizen while they hold LPR status. However I have not been able to find any relevant case law.