If you want a truly 100% free and open-source tool without any pop-ups, 7-Zip is the most highly recommended alternative. It is more lightweight than WinRAR and supports almost all the same formats.

Most sites claiming to offer "cracked" versions are actually distributing malware, ransomware, or spyware disguised as an installer.

WinRAR officially offers a 40-day trial period. However, unlike most software, it when the trial expires. You will simply see a pop-up notification asking you to buy a license, which you can close to continue using all features of the program for free. Why You Should Avoid "Cracks"