Hey folks,
I've got one of these door latches I'm wanting to install onto our front door - yet another 10-minute job that I've hit a hurdle with.
https://www.bunnings.com.au/syneco-chrome-door-guard_p0223207

The door frame is metal over a brick wall. When I drilled this hole:

There was about a 30mm void inside the frame, between it and the brick behind it. I expected to find solid brick so had planned to insert lugs and screw into them, but the void means there's nothing for the lug to hold onto (side view below).

I considered using pop rivets instead, but thought I'd run this past the community here first in case there's a better option. I'm concerned that pop rivets wouldn't offer as much strength as screws etc, especially considering this is supposed to be a security device...!
Any suggestions appreciated, thanks a mill in advance 😀
Cheers, Danny.