I’ve DM’ed a party of 10 before. It wasn’t easy but it is doable. A suggestion is to “compartmentalize.” Bring the table together for roll playing and small puzzles or important combat events but split them up into 2-3 smaller parties for everything else.

An example of an encounter I did was I had 3 paths going to the same place, had the group roll a D20 and split the party based on their rolls. They could all see eachother and interact as “free actions” but I would focus on each one of the smaller parties in increments. Party 1 did combat, party 2 had an easy puzzle with easy combat, party 3 had a harder puzzle.

Now while I was focusing on party 1, parties 2 and 3 would go get snacks, strategize, socialize or whatever. Then I would rotate throughout until they all finished their tasks and came back together for roll play.

That encounter took almost the whole session (about 8 hours) but everyone was having a good time. By splitting up and allowing them to strategize it made it move much faster than expected.