Everything is working, so this is a quick update to list the location of all the resources to duplicate this project:

Here is the page to have the boards made at PCBWay:

https://www.pcbway.com/project/shareproject/Tile_Board_for_A_Seven_Segment_Display_Art_Installation__v8_.html

The seven segment displays are:

https://www.aliexpress.com/item/10PCS-0-56inches-7-Segment-1-Digital-LED-Display-Super-Red-Common-Cathode-AUG-18-Dropship/32914934580.html

Here is the code that runs on the Master Arduino. Its job is to send the desired content to be displayed down the line:

https://gitlab.com/arduinoenigma/seven-segment-art-installation/tree/master/Board100x9x13-Master

This is the code for the tile boards. It receives commands, processes and relays them down the line to other boards while continuously multiplexing the displays:

https://gitlab.com/arduinoenigma/seven-segment-art-installation/tree/master/Board100x9x13