Hello David Vescovi,
The i.MX8M Mini itself has a termal sensor integrated. You can find more details on the Thermal Monitoring Unit (TMU) section of the i.MX8MM Reference Manual (link below, you may need to login to download this document).
https://www.nxp.com/webapp/Download?colCode=IMX8MMRM
Software wise, there is a Thermal Driver that polls this TMU and acts accordingly. You may find more details about this on the i.MX Linux Reference Manual that is available as part of the Linux BSP Release Documentation.
I hope this helps!
Regards,
