I deleted enough to have 3 gigs on my iPad but it still won’t download any updates. What can I do?

It will offer iPadOS 14.8 but that does not yet involve downloading that compressed installer, expanding that installer, and the temporary storage necessarily consumed during the installation. You will need more than 3GB available on the iPad to receive and install this package.

If it offers iOS 14 and nothing newer as in iOS 15 - there is the answer. The iPad does not Qualify. If it did Qualify - it would offer iOS 15 which one indicates it does not.

If you need more space for an update on your iPhone, iPad, or iPod touch

Update your iPhone, iPad, or iPod touch and if nothing is presented - the iPad is running the latest version of iOS it Qualifies to run