Proposed property tax notice for mineral right owner

Thanks for the info. Thru the years, as me and my mom tried to learn more about her mineral rights and the rest of the family, Noone mentioned property taxes when working with leases or when discussing production possibilities on leases. So this comes as a shocking surprise.
I tried the address several times, maybe something on my end, as it still doesn’t work. I had already pulled up assessors.

The other curious thing to me is on the postcard it shows 2021 “Proposed” property tax. Proposed is a curious word.

What I have read in Texas tax laws, so far today, it seems if you make less then 500 dollars a year, reference producing wells, no property tax is assessed. But still trying to learn more. It just blows my mind , property tax, on mineral rights.
Hmmmm