- Yes, you can adopt AP300s using any 5.X version until 5.5.6, which it was the last one supporting AP300 adoption. After 5.7 we removed the capability of adopting and manage those APs, as AP300s are EOL/EOS (mentioned on the PMB2484).
- To adopt those APs you will need enough AP licenses (not AAP licenses). Meaning, on RFS4000s you will not be able to adopt more than 6 APs, as you cannot add more than 6 AP licenses on the controller.
- Please refer to the following article to understand the difference between licenses: What are the differences between AP and AAP on WiNG v5.x?