As someone who also struggled with this I'd say that just a simple "hi" will most likely already do. The one person I matched with on a dating platform (my current partner) said I was the only one that just simply said hi instead of trying some cheesy pickup line (or immediately talking about sex).
As mentioned above, I struggled with joining an online dating platform for a long time and when I did it took me a month of active swiping before I finally got a match. I was really nervous but I acted a bit more confident than I was (at first at least, before opening up later during our first date) and we've now been together for over 5 years.