I realize Markkanen is just speculation, but despite the need for a stretch four, I wouldn't bother. The Bulls are clearly at the very least open to moving him, but they won't let an asset walk as an RFA without overpaying and he's not worth it. Injury prone, inconsistent, sub par defending center sized "power forward" is an awkward archetype.
I don't buy the Allen rumor at all. He'd require extreme overpayment to get the Cavaliers to consider not matching and the Spurs are obviously not doing that when they have a slightly older and what will be a significantly cheaper version, in Poeltl.
If the rumors of the Hawks being open to moving Bogdanovic and Reddish are true, I'd first try DeRozan, Lyles and Walker IV for Collins, Bogdanovic and Snell. Failing that, I'd try DeRozan for Bogdanovic and Reddish.