Keep it in a safe, trigger locks are a joke.
You can load a round in most firearms, and still use the trigger lock to discharge the round.... (there are many reports of this happening in the news in the past, even though many states "require" them) The cable locks are better, but nothing beats a safe. A true safe.. not the cheap bio lock or button combo to open safes. (ALL can be disabled easily, Bio lock can be reset with a paperclip...) The trigger locks can be easily picked, or pried open with a simple screwdriver. or if not completely tight on the guard.. can be moved to press the trigger.
On most firearms, you can install a trigger lock and THEN insert a round into the chamber. you now have a loaded firearm with a metal rod next to the trigger... Put a trigger lock on a revolver... open the cylinder and insert a round (or 6) close cylinder and cock the hammer.
How do you safely remove the rounds? can't open the cylinder now... can't release the hammer.. you must remove the lock. Insert a key, connected to a metal rod that sits right next to a trigger that is already halfway depressed...
Now picture a child who has watched someone on TV load a revolver do the same..
*some* firearms trigger guard designs prevent the "lock" from being inserted "correctly" so they are much easier to discharge with the lock on than others. All of the trigger locks are designed the same and they all have the same warning in the fine print saying they are not effective on all firearms.
Remember Cooper's Four Rules
1. All guns are always loaded.
2. Never let the muzzle cover anything you are not prepared to destroy.
3. Keep your finger off the trigger til your sights are on the target.
4. Be sure of your target.
A trigger lock violates #3, but gun control advocates claim it's "safe"...
Finger or metal rod, it doesn't matter. NOTHING goes inside the trigger guard.
I know some people swear by them as being safe, I will never do so. You purposely put a metal rod next to the trigger and compromise the most basic gun safety rules.
The cable locks are much better, but can be also compromised with a pair of pliers. Search youtube on how easily the single gun locks/safes (Bio safe, button combo safe, etc) can be disabled. If it's on youtube... a child can find it as well.
There is no all in one solution that will work for every model of firearm ever made, except education and a real safe.
(not meaning to start an argument, and I know some will disagree with the above..)
IMO everyone who decides to own firearms, should also buy a shotgun! So versatile.