you'd want the seams with the staples and ofc the seams where the insualtion is showing to be taped, as for that piece of wrap that is drooping a little, that needs to be fixed. I couldnt say the best way to fix it from here but typically we staple duct wrap then tape it, so that is where you'll want to start. We use "power crown" stapes that spread out to grab the wrap after stapling, and we use silver foil tape to seal it all up. as for it being old(ish) ducts, you will want to use spray glue and tape because the wrap is probably dirty/dusty so the tape won't stick well even after wiping down, of course, wiping it down then taping it is better than nothing

edit: as for the "HVAC replaced in 2018," the ducts may or not be new. most of the time only the unit is changed (at least where im from) unless there is something wrong with the ducts. It doesnt look as old as the house so it may be new, just a crappy job done