2021 Apple Mac mini M1 does not currently support any external graphics
Check out my previous article on Apple Silicon M1 + eGPU
Apple worked with Blackmagic Design to build the eGPU and eGPU Pro in 2019 to increase graphics processing capabilities for all Apple Mac products is unlikely to be a waste of time now Apple Silicon M1 is available.
The 2021 Apple Mac mini M1 has two Thunderbolt 3 / USB 4 ports capable of delivering 32 Gbps of PCIe 3.0 x4 connectivity.
AMD graphics support Metal; however, Apple could be working on providing an external graphics module with the graphics chip from the M1 SoC.
Quite quickly, a Mac mini M1 could be equipped with two eGPUs for a total of three 8-core GPUs supporting six 6K displays.
6 x 6016 x 3384 = 122,148,864 pixels