Please help! Suffering from this car...

[fcool]

We bought a 2017 XC90 T6 in November 2021 with 60k miles on it. Now it's over 80k miles, and I just did an 80k maintenance check in May 2023 that cost almost US$1k: replaced the rear brake pad and other things.
And it began... we're in Florida, US, and the AC suddenly stopped working. An authorized dealer shop said the evaporator's leaking—cost US$172 for just the diagnosis. We evacuated the AC twice for a diagnosis and recharged it twice, of course, and every time it was recharged, the cold air lasted for about a week. When the weather was really hot, the AC issue got worse—once, the barely cool air turned even warmer when the outside weather hit almost 100 degrees F. Also, the front heated oxygen sensor is not working. The quote for repair was over US$4k.
A few days after the diagnosis, I heard a high-pitched squeal noise coming from the engine bay whenever I released the gas pedal. The noise lasts the whole time the car's on the cruise control. It seemed whenever the car attempted to remain at the same speed, the noise occurred. I drove the car just commuting for a couple of more days, and the noise has become louder and is now undrivable. Please check the attached video. It's really frustrating that I've been having all these issues a few months after the 80k maintenance check.
Do I really need to go to the authorized dealer shop to fix it? Could this noise be because they did something wrong when diagnosing the AC issue? I researched that high-pitched noise can be malalignment of some belts or worn-out bearings.... Would I be able to ask for a supplementing diagnosis for this noise?
I have almost zero car knowledge, and I'd really appreciate any advice about this issue. Thank you!

[Oly850]

Hey I get it. We have a 2017 XC90 Inscription as well, but ours has really low miles around 32k. We’ve done tires & brakes & oil changes, and one warranty repair to a plastic cooling hose join.

If you’re mechanical, swapping an O2 sensor is a piece of cake with a O2 sensor socket you can get at a local auto parts store, maybe you have a friend who is handy this way?

As for the AC, stay away from the dealer, I’d find a reputable independent shop and have them find the leak which can be done with fluorescent dye. It may be as simple as an o-ring in a hose, could be worse. I’d rather throw $300 at an independent shop and fix the leak vs having Volvo rip out the whole system which is all they know how to do.

Post updates!