i have tested, no problem with analog input for mqtt, i think maybe some details you set not correct. you can check with my setting photos, just set as my photo.
KCS V2.0.1 firmware:
KCS_KC868_A4_V2.0.1.zip (Size: 764.49 KB / Downloads: 152)
KCS V2.0.1 firmware:
KCS_KC868_A4_V2.0.1.zip (Size: 764.49 KB / Downloads: 152)