According to Circana (formerly NPD) via industry analyst Mat Piscatella, it debuted in second place right in the "Top 20 Best-Selling Premium Games" right underneath Ghost of Tsushima and just ahead of Call of Duty: Modern Warfare III (2023).
"Ghost of Tsushima generated a slightly higher consumer spending total across physical and digital game sales than did physical-only sales of Paper Mario: The Thousand-Year Door (Nintendo is not a digital data sharing publisher)."
The one other first-party Nintendo game represented in the top 20 best-selling games in the month of May was Mario Kart 8 in 15th place.
"The May 2024 Console spending declines versus a year ago across hardware, content and accessories spending can be partially attributed to the strength of the launch of The Legend of Zelda: Tears of the Kingdom in the May 2023 comparable period... May video game hardware spending declined 40% when compared to a year ago, to $202M, and is now 30% lower YTD. Through May, all current generation hardware platforms are showing double-digit percentage declines year-on-year in 2024, with Switch showing the most significant drop."
If you haven't played Paper Mario: The Thousand-Year Door before, the Switch release is a great chance to give it a go.