It depends how the settlement level of the contract is determined.
If the excahnge determines the settlement level based on something linked to the physical market (for example ICE Brent futures final settlement), then the settlement level before the expiry of the future can trade wherever it wants, based on the vwap in the window. But if you hold the future to expiry, then it will settle according to the ICE Brent Index, which is (in a somewhat convoluted way) linked to the physical oil price in the north sea. In this case, it doesn't matter if where the futures trade*, since the value is based on the value of oil and not on the value the futures trade at.
ETFs can also trade at a premium or discount to their NAV, depending on suply and demand essentially (for example, see here to read about the premium/discount on the GBTC etf).
Here is another interesting story about the DGAZF etf going from \$400 to \$24,000 in a number of days, on basically no volume, and no related move in natgas.
Another example from last year happened when the physical gold price because detached from the futures price - this is because the contracts are not the same, as the gold futures are physically settled in new york, while the physical gold price is set in london - there are infrastrcutural contraints to moving gold between the countries, as well as changing the format of the bars acceptable for delivery. Last year during the height of covid, these infrastructure issues because even harder to solve and allowed the gold futures price in new york to deviate from the physical value of gold set in london.
The important differences in these examples is in how you're able to turn your holdings back into cash, and additionally what liabilities they can provide you with.
*However, it's worth bearing in mind that if the futures trade significantly above the actual value of oil, then someone able to trade the physical market may step in and sell the futures while buying physical, where they'd be happy to buy physical oil at any price up to where they can sell the futures, so the spot may be lifted in this scenario.