https://wccftech.com/m1-mac-models-connect-up-to-6-external-displays/

With Thunderbolt 3 ports present on all three M1 Mac models, users can still experience a ton of throughput, with the exception of connecting external GPUs that is. While Apple claims that users can connect a single monitor up to a resolution of 6K at 60Hz, one YouTuber has found a way to connect up to six external displays. Yes, that’s correct; six external monitors on these M1 Mac models.

Ruslan Tulupov discovered that it’s possible to hook up to six external monitors on the M1 Mac mini, and five on the M1 MacBook Pro and M1 MacBook Air, but it will involve the use of DisplayLink adapters. When the M1 Mac's display ports have been used, DisplayPort adapters need to be connected via an external dock to provide more ports for the additional monitors. However, users will need to be careful about running those monitors at higher resolutions because sooner or later, you’ll run out of bandwidth from the Thunderbolt 3 and remaining ports.