I’m having the same problem on the mac version (Version 9.2.18 (9.2.18) with the dual monitors appearing in the same main window with no ability to switch.
I’m connecting from a 13 inch Macbook m1 set to 1440 x 900 resolution to a Mac Mini M4 with 2 LG 4k UHD Ultrafine monitors (27US550-W) both set at 2560 x 1440.
They are set that way because of the Mac scaling issues with 3840 x 2160.
One monitor is connected to the computer by HDMI, the other monitor goes to an HDMI switch 4k@60hz splitter, bidirectional switcher which serves as the second mac mini monitor and a single monitor for my Linux box (depending on which channel is selected 1 or 2).