You can look to retrofit cables, or… My truck came with a crease in the tailgate from someone opening it onto the bumper, I recently did a complete tailgate restore/repaint/ on that…
Since I dont want to be that guy that expects his wife or friends never to make the innocent mistake of not chaining it flat if they open the gate when I’m not looking.. I went with the MarK folding straps option, which require notching the inside edges of the tailgate, still have the chains to lock it when up, kinda would miss the exterior chain look though there are latch options out there, but as always, personal choice……. Me and the wife tend to open it and sit and picnic at the few events we attend, so a strong strap and PPF made sense… each their own Ps, wife thought I was nuts to cut, punch, edge dye & stitch up the chain covers from some leather I had around…..an hours work, she’s prolly right…