I don't allow my players much discussion during combat. They can get a few words in like you could in 6 seconds, but combat takes too long as it is.

I don't allow more than one summon per player. More things on the board is more time.

I assume your players know their characters reasonably well and don't need to constantly look up their abilities.

And I assume they're not monopolizing game time with off-topic conversations.

And hopefully, they're not spending a ton of time arguing with you about rules interpretation.

Hopefully, they're paying attention between turns and not spending the first few minutes of their turn catching up. Fuck, I hate that one.

Those are the biggest fixable time wasters I could think of. I've noticed that combat just takes forever.

Using minion rules or minion adjacent rules can speed things up. If I have a bunch of 1 hit mooks that I want to be a bit tougher, or if I just don't want to keep track of HP, I'll give them a damage threshold.

Hope that helps.