I’d like to say Linux is a viable Windows alternative.
It isn’t.
On the consumer side, the A-list video game studios do not release their titles for Linux.
On the business side, Linux lacks anything like Active Directory that I’m aware of. Samba doesn’t count. It’s an incomplete implementation.
AD is based on LDAP. There are several open source LDAP products. OpenLDAP and ApacheDS are alternatives that I have seen customers use