As you said Windows S mode only allows applications to be downloaded from the Microsoft store, it's all the same OS with some restrictions applied. With there only being the remote access version in the store that's all you can download in s-mode.
You can switch out of S-Mode but this is one-way so you can't go back after doing this.
To do it go to Settings > System > then on the right-hand side click "Activation". Click on S-Mode and expand it, then click "Get" to upgrade to Windows 11 Home (free), or Windows 11 Pro.