The most likely reason is that the firmware on the Pi could not fetch the required files from the SD for some reason. The square is the default unless disable_splash=1 is set in /config.txt. Info-beamer sets this, which suggests it’s not read during boot and everything falls apart.
Can you try setting up the SD card using the RPI imager tool? You can select info-beamer from “Freemium and paid-for OS / Digital signage OS / info-beamer” or use the .img.gz system file from https://info-beamer.com/download.
Thank you for the quick response. Unfortunately the same issue when using RPI imager. Tried to format using it first, writing, and verifying is confirming OK as well. Think I have to conclude this is a SD card issue, and that the PC reads it OK but not the pi.