Since the ssh client is pretty ubiquitous and has been included with Windows 10 installations for the past couple years, I’ve discovered it can be a useful tcp port scanner if you use the verbose flag:

For Windows:

ssh -p 80 google.com -v 2>&1 | findstr Connect

ssh -p 80 -o ConnectTimeout=1 www.google.com -v 2>&1 | findstr Connect
debug1: Connecting to www.google.com [142.250.191.228] port 80.
debug1: Connection established.
kex_exchange_identification: Connection closed by remote host

As for your *nix systems, just use grep instead of findstr. I hope someone else finds this useful!