Just to clear things up, you have the Opal Kelly version of the board and you installed the Rhythm Plugins from Plugin Installer and then used the "Acquisition Board" plugin instead of the "OE FPGA Acquisition Board" plugin, right?
Also, can you share the signal chain config you used when the GUI crashed and the log file from the crash as well? Log files are located in "C:\ProgramData\Open Ephys\configs-api8" (ProgamData is a hidden system directory).