There's always velcro? Though you may not want to attach it directly to the wall because of paint, you could probably use it to attach something for hanging, to the back. I recently mounted a nearly 10lb, 48"x24" white board directly to a metal door with a single package of adhesive mounting velcro. It wasn't even intentional, I had a whole over-the-door hook plan worked out for its mounting holes, using the velcro to keep it level and from any movement, and it turned out to be plenty, shockingly strong enough.

It's actually got me super excited for more hanging of weird things, cause I've gotten pretty good with Command Hooks, etc, and often find them wanting... Literally tonight, though I can't prove the timeliness, had one fall off the wall, that wasn't holding anything heavier than its load, just an old walking stick. Eventually, they die, and it seems the newer adhesive quality has become subject to enshitification, but I may also be a cynical shite. (งツ)ว