How do I bulk close tabs on a 5th gen iPad?

Just to offer a little clarity, perhaps....

There are two ways to open a new tab on the iPad. One is to tap on the + sign. Long pressing in that icon will not work. That will bring up recently closed tabs.

The other way to open a new tab is to hold down on the two squares icon to bring up the contextual menu. That is the one that you want to long press in order to close all tabs at once.

iPad5 supports iPadOS 14.3 (current).

If the iPad is updated to the current version, you’ll be able to simply close all Safari tabs from a long-touch of the new tab icon - and from the menu choosing Close All nnn Tabs (highlighted in red)