HVAC return DIY-able?

Was down in the crawl space today and noticed that one of our returns appears to have the elbow pulling away from the plenum. It looks like it used to be taped. Me shining light on it to get this pic makes it hard to see, but I can see light in the crack above the 10 26 stamp. We’re in a split level and this is one of two returns. This return is in the floor of our main room - used to be in a wall but that wall was taken out in a remodel 5 years ago.

I am an amateur home DIYer. I do not have anything approaching HVAC knowledge and would def not try to DIY anything electric in the system, but this \*appears\* to just need some tape…? And I would like to be competent with duct maintenance.

In my ignorance, am I missing anything that means I should keep my good intentions to myself and have a professional look at it next time we have someone out? Does air leaking here even matter?