Mqtt integration chirstack

Could you help me with Mqtt integration setup?
I have my server working fine after installing Chirpstack following the procedure for Ubuntu OS. I registered first gateway and device and added successfully integration with Cayenne.
I tried integration with Mqtt but it doesn’t work.
Is Mosquitto installed by default a possible cause or the only setup that I have to work on io on the ui application server ?

I have another question but won’t open a new topic. Everything works fine. Know I tried to do the mqtt integeation. But there is only the possibility to get certificates.

In my project everything works on one server. So I don’t won’t certificates…