“… the hotel we will be at has Tesla superchargers.”

To be clear, Tesla Superchargers are “near” the hotel, they are not part of the hotel services. I’ve stayed in places where the Superchargers are right in the hotel parking lot, I’ve also been to a hotel that claimed Superchargers but they were two miles away. FYI

“… Can an EV6 use the Tesla chargers?”

No! Okay there are a small handful of magicdock capable Superchargers but they are rare and unlikely in the extreme.

" - Will we have to download an app to use the tesla charging network?"

No! With Tesla it’s very simple, just plugin. No fuss, no muss, no apps. The rental agency will be billed for the charge and they will pass it on to your bill.

Not asked, “How do you find the chargers?”

The Tesla will tell you where the chargers are located and recommend one based upon your charge status. Selecting it from screen will offer to auto route you to it and automatically begin preconditioning the battery for fast charging.

Based upon your unfamiliarity with EVs, I strongly recommend you go Tesla and only Tesla.

Part of Tesla’s normal purchase procedure is a series of brief training videos. These videos are available via Tesla and Youtube. I suggest watching them before your first drive. If you have time, schedule a test drive with your nearest Tesla showroom. It’s fun and there’s no obligation or cost.

If you go non-Tesla:

You cannot use the Tesla Superchargers.

You will need to download apps for charging and possibly apps to even find the chargers, depending upon the car. You may have to know to manually pre-condition the battery or be completely unable to do so, depending upon the car. I’m not familiar with the EV6 amenities.

Caution!

Rental agencies have a long tradition of not having the car you reserved and offering an “equivalent”.

Often rental agencies require you to charge up the car before returning it. Look carefully at the penalty and decide when the time comes what the effort is worth to you. Depending upon location support and contract details, it might be worthwhile to just pay the small penalty.