树莓派使用的ARM处理器是64位的，在安装了32位Linux操作系统后，默认模式设置为64位模式

https://github.com/raspberrypi/firmware/issues/1795
The switch to running a 64-bit kernel by default on Pi 4 is intentional. We believe it gives a better experience with few drawbacks. As you’ve found, you can revert to the 32-bit kernel by adding arm_64bit=0 to config.txt.

sww@raspberrypi:~ $ uname -a
Linux raspberrypi 6.1.21-v8+ #1642 SMP PREEMPT Mon Apr  3 17:24:16 BST 2023 aarch64 GNU/Linux

如果需要将其设置为32位模式
需要更改/boot/config.txt, 在[cm4]下添加arm_64bit=0

[cm4]
# Enable host mode on the 2711 built-in XHCI USB controller.
# This line should be removed if the legacy DWC2 controller is required
# (e.g. for USB device mode) or if USB support is not required.
otg_mode=1
arm_64bit=0

重启后，则使用32位模式

sww@raspberrypi:~ $ uname -a
Linux raspberrypi 6.1.21-v7l+ #1642 SMP Mon Apr  3 17:22:30 BST 2023 armv7l GNU/Linux