Tenant Disappeared, how to deal with eviction

[Carlos Chavez]

Hi, looking for some advise...

Tenant is behind on rent, tried working with tenant during the pandemic on a payment plan. Beginning the year is nowhere to be found, although all their belongings are inside the house. I would like to just get the keys and forgive the debt or even probably do a "cash for keys", although as mentioned before, tenant is no where to be found, and her emergency contact (ex-husband) does not know either where she is. He said that he would be willing clean up the house and get everything out, can I get him to sign an agreement to break the lease on her behalf and turn in the keys?

Worst case, how do I serve an eviction notice? what if the tenant never responds to it? can a get a law enforcement office and get in the house? 

This is in Dallas, TX. by the way...

Thank you in advance!