Hello, I need help with a setup involving these two devices. I have an AP L22UGS-5HAXD2HAXD with version 7.18.2 and a CPE SXTSQ 5 AC DC with the same version. I want to create a station bridge, but when I apply the station bridge mode on the CPE and scan for the signal, it finds the one generated by the AP. However, as soon as I accept the connection, it automatically switches to station mode. Is there something that needs to be configured on either of the devices beforehand?

Which package do you have installed on SXTSQ 5 AC: wireless or wifi-qcom-ac? Your mANTBox ax 15s runs wifi-qcom and that one is not compatible with wireless when it comes to various *-bridge modes.

OTOH, SXTSQ 5 AC has only 16MB flash which is pretty tight for routeros+wifi-qcom-ac when ROS is 7.18.x ... so you may get into a dead-end if you decide to go this way.

The SXTSQ 5 AC has the wireless package. In this case, is it not possible to install the wireless package on the mANTBox 15s? It accepted the configuration in station pseudobridge mode

wifi-qcom-ac does support bridge configuration ... it's just not compatible with wireless' bridge mode.

And no, wireless package support for radio hardware ends at AC-class devices. You can't install it on AX-class device such as L22UGS-5HAXD2HAXD.

station-pseudobridge doesn't require any special compatibility from AP, it can work even with APs from different vendors. However it's not trully transparent (hence pseudo...) and that might bite you later.
More about different station modes and their peculiarities: https://help.mikrotik.com/docs/spaces/R ... tion+Modes