Attempting to simulate AXI3 Master BFM in Qsys system. "Library mgc_axi_master_10611 not found."

Can you try the modelsim starter edition? https://www.intel.com/content/www/us/en/programmable/downloads/download-center.html

If you are using Q18.1 you need to simulate with the modelsim that support Q18.1.

Modelsim starter edition require no license, the example should work because I had try it in the older version and with Modelsim starter edition.