The Cliqz Browser is a fork of Firefox. The last version of Firefox for Windows XP was 52. The last version of the Cliqz Browser that was based on Firefox 52 looks to be 1.12.1 based on their release history on github, I'd suspect that is the last version that runs on XP.
It is unlikely that it will treat untrusted Certificates any differently than Firefox. Aside from being based on Firefox, it is a fork that is designed to strengthen security and privacy considerations; ignoring untrusted security certificates certainly goes against that goal.
Realistically, what you need to do is to update the installed root certificates on the system in question. I linked to a Windows XP hotfix in another thread which is also described
here.
Browsers that support https aren't typically going to ignore a SSL certificate that it cannot verify. More recent browsers have certainly made it harder for people to ignore untrusted certificates, but that is because making it easy causes many users to become victims of their own hubris.