Unlike many other apps, Threema offers two main ways to get a license:
If you are buying for a group or a business, the Threema Work tier offers volume licensing which significantly reduces the cost per user.
While I understand you're looking for a "free top quality" license key for Threema, it is important to clarify how the app’s licensing actually works and why you won't find legitimate keys being given away on the open web.
On iOS and Android, if one family member purchases the app, it can often be shared with up to five other family members through official "Family Library" or "Family Sharing" features.
Your data is protected by some of the strictest privacy laws in the world.
If the cost is a barrier, there are legitimate ways to get the app without resorting to risky "free" sites: