Are these bare prints?

Not surprising for metal but surprising in the context of a high quality artwork print can take quite a bit of abuse.

Chromaluxe has semi gloss and matte finishes. It’s probably just that your particular lab doesn’t carry them but others do.

Direct to dibond is probably a UV printer.

In terms of quality of your three options, id rank them (1) paper print mounted on dibond, (2) chromaluxe and (3) direct UV dibond.

Paper is definitely the best quality but chromaluxe can still look very good too. UV printing is not as high quality but may be good enough for you. If your lab is local go in and look at samples.

Stay away from brushed metal prints unless you’ve seen it before in person. It’s a very niche look and doesn’t work for many images imo.

The reason I ask is because I am thinking of making some large prints, like 40x60 or larger, but am not sure what to do once I get them.

I think this explains the popularity of ready to hang art like metal prints which don’t need a frame. Metal is surprisingly robust and although pricy, aren’t as pricy as having a paper print framed. If it was smaller, I’d frame it myself but a 40x60 isn’t something I’d attempt.