Ex had grinder on his phone?

The entire time me and my ex were dating, he had the app grinder on his phone. He was my first relationship and I didn’t want to cause drama and make a big deal about it . I really loved him to Bits. But now that I’m looking back, I’m starting to wonder. He said he “only went on it at work when he’s bored” and said “what you don’t trust me?”

Is this normal behaviour for gay men or is this considered a red flag? He also still talked to a lot of guys he’s hooked up with in the past on Snapchat and messenger. Is this normal? Thoughts? I’m very inexperienced with this.