It can be a bit difficult to do Wi-Fi penetration testing with tools like Aircrack-ng without having a Wi-Fi card that supports monitor mode, although it's not impossible. Here are some options:
1. Emulators and Virtual Environments: Use the Wi-Fi emulation tools to simulate network traffic without having a Wi-Fi adapter. For example, Fluxion allows for the emulation of an access point by creating an "evil twin" attack that entices clients to connect. It is not suited for the capture of real network traffic but can provide useful practice scenarios for testing.
2. USB Wi-Fi Adapter with Monitor Mode: Although this is more of a circumventing measure, using affordable monitors mode-supporting and packet-injecting USB adapters can make the entire thing less strenuous. Alfa AWUS036ACH or any other Aircrack-ng-supported USB adapters, which can be fitted right to your laptop or PC's USB slots.
3. Using Virtual Labs such as GNS3: If you are looking to train more generally, more to the point of attacking WiFi rather than penetration testing, you could use network emulation software, such as GNS3. GNS3 won't help you to capture real handshakes on Wi-Fi but it's an amazing environment in which to simulate network security-related scenarios.
4. Software-Defined Radio (SDR): Another way you might be interested in doing SDR-based Wi-Fi testing using something like HackRF or RTL-SDR. They're not actually Wi-Fi adapters, but you can capture and analyze the wireless signal in modes that are similar to monitor mode. Of course, setting up an SDR is more complex setup; it will let you play with some wireless frequency bands you will see increased scope in your tests.
5. Simulated Networks and Captive Portals: In order to get a feel for some of the basic WPA/2 cracking techniques without live packet injection, work from pre-captured .cap files available over the internet for educational use. Several platforms, including Kali Linux, offer network labs where you may simulate capturing handshakes or password cracking, all without having to have a physical Wi-Fi adapter.
6. Emulation of a local network: mdk3 can be run on some local networks without any Wi-Fi adapter, emulating a deauthentication attack or DoS attacks, though it's pretty limited compared with the dedicated Wi-Fi card setup
