I keep hearing that it's possible to use any other object as mean to reach Jhana other than the breath...

HOWEVER,

I have tried using the titinus sound like you hear at your head when you are at a quite place... I can stay on that sound without a thought distracting me or any other external or internal thing... but I never ever feel any effects from it

When I use the breath as attention to focus on, even when my mind is a mess and I get distracted a lot, I can still reach blissful states

I know plenty of other people who meditate on that sound, and they don't get Jhana like experiences as welll...

I think part of it might be that when you close your eyes and hear/feel the breath, it is an object that is taking place inside your body, so it fucks with your proprioceptive sense in a rapturous way.  That would account for the ''blissful states'' you can reach, "even [while your] mind is a mess."

Just an aside, some schools of thoughts would not consider this to meet the criteria for "first jhana," since Rapture is present but Sustained Thought is not (I associate these factors with the continuity and stability of attention that Culadasa talks about).  This also means that I can't do first jhana consistently  but I'm working on it!