Is it possible to setup always on QL Server 2016/2017 without windows clustering and domain? My intention of implementing always-on and secondary replica is offloading the select query from the primary database server.
Yes, it is possible but will require SQL Server 2017 (I'd also apply the latest CU, which at time of posting is CU4).
Please note that without a domain, SQL Authentication is the only available authentication type and there is also the additional endpoint setup of using certificates.
If you'd like to read more about read-scale availability groups (Not for HA or DR) the Docs articles are a good start. I've also blogged about it when it comes to things like read only routing.
I'm not expert at windows clustering [...]
You really don't have to be since you're not looking for HA or DR. That's my opinion, though, and won't translate well everywhere depending on the resources and familiarity with Windows Server.