Mitch,
Yes, the latest version of the Radioddity copy of the firmware for the X6100 is indeed the ZIP file that you got, that ends in "[fix CAT]." The file that you then download is titled, "Xiegu_X6100_Firmware_Upgrade_20230831.zip" not the one titled "Xiegu_X6100_Firmware_Upgrade_20230807.zip."
When you get it installed properly, the Base should have the date "V1.1.6 Mar 7 2023,09:57:03"
Install the firmware from the SD card using the upgrade instructions in the Firmware Upgrade Tutorial. After you install the firmware from the SD Card in Step I, you need to make sure you are using a 13.8V power supply to power the X6100 before proceeding with Step II. The power supply must have enough current capacity, probably 3 amps or more, to complete Step II successfully. You probably can't use the charger that came with the unit, since on mine at least it only supplies 12.00 volts and about an amp maximum.
If the Base firmware installed correctly, it should have the Mar 7 2023,09:57:03 date.
From what you said in your post and from the picture, you may only need to perform Step II. First, turn off the Charging in the menus. Then turn off the X6100 and attach the 13.8V power supply. Then follow the instructions in Step II.
Hope this works for you,
Jerry K6ANI