Can the new M1 iMac mini support 2 external monitors? If yes, how?

The M1 Mac Mini only supports one USB-C monitor.

You can try the Apple Digital AV or Belkin USB-C to HDMI adapters that Apple sells in reverse and an HDMI cable, but to be honest I haven’t personally tested them.

USB-C Digital AV Multiport Adapter

https://store.apple.com/xc/product/MUF82AM/A

Belkin USB-C to HDMI Adapter

https://store.apple.com/xc/product/HKQ22ZM/A

Please clarify what you're talking about. There are iMacs, but the M1 iMac won't be shipping until 30 April, it hasn't been released yet. Then there are M1 Mac minis, but there is no such thing as a M1 iMac mini.

If you're talking about the M1 Mac mini:

Yes.

What monitors do you have?

One monitor needs to support HDMI and connected the HDMI port using an HDMI cable.

The other monitor can be USB-C using a USB-C cable or HDMI using a USB-C to HDMI adapter and HDMI cable.

Yes you can connect one monitor on a USB-C port and one monitor on the HDMI port.

see > https://support.apple.com/guide/mac-mini/connect-a-display-apd8e4fbbb97/mac