I didn't find any tutorial using mac ports to install pyodbc on a mac with m1, so here is my way, maybe it helps somebody. My goal was to talk to a MS SQL Server.
If you want to use Homebrew instead or more information please look here https://gist.github.com/Bouke/10454272
The only dependency you are going to need is freetds, it will install automatically it's dependencies.
BUT because we later on need the shared object file libtdsodbc.so you need to install it with as the variant +odbc.