I need my phone to log into everything...

I always see these posts about ditching smartphones and going back to flip phones that only call and this and that. I assume these people don't use auth apps or phone 2FA. If you don't need them to access work or have a non cellular device just for apps then maybe you can sneak past this.
We just nuked a couple of streaming services in order to get HBO again so we could watch the Sopranos. (He watched all of it years ago but I've never seen it.) In order to log into the app on the TV I just have to point my phone at the QR code on the screen and log in from face ID. That type of use case is really helpful when your password is two dozen characters of keyboard vomit that you honestly do not know and the only way to type it in is selecting each letter/item with that on screen keyboard and the D pad of the remote.
I like using my phone as the login device for simple stuff like this. For real serious accounts I use auth apps and such. You can use a YubiKey on your laptop or whatever too. But I can always go grab my phone if I need to log into things if my main laptop isn't around.
Switching to a dumb phone for me means a phone that doesn't have access to modern apps. When my boys first got phones to use at school (Sports and Band don't communicate with parents directly, they have the kids call/text when practice is over or they have come back from an event.) we got them what I consider dumb phones. They had a keypad and the ability to text but nothing else. This only became an issue when school activities required access to a Remind app that wasn't available on them. They only needed the phone to call us to come get them or if practice was cancelled but the coaches/directors couldn't communicate with them in their app groups.
Which is why when I see folks talk about going back to a flip phone I have to wonder how they navigate their work day or communicate with anyone else (outside calling/text obviously). It's fun to pretend it's 2004 but restaurants use QR codes to order/pay. Farmers markets take CashApp/Venmo. Parking lots use apps to pay for spots. Some large venues and events are 100% cashless meaning your card or phone better have tap to pay. Most of us can get around easily without our phone navigation in the car, but not so much in a place you've never been to.
I would assume modern "dumbphones" have better cameras than they did 20 years ago and can access most "apps" via a browser. You can't even use many of the original flip phones anymore because they are on the 2G/3G networks that are no longer live. I still have a working Motorola Razr. Working as in it turns on and you can play snake. Even with an adapter the SIM card wont take a modern one, and ultra modern phones don't even have physical SIM's anymore to swap from device to device. A ten year old Ford Focus has better resolution on it's backup camera than this thing. (The phones camera wasn't good back then either it was just cool to have.) The browser is so out of date modern sites wont render. It's just a fun toy these days. And at least my N-Gage can play games.
I think for most people wanting to do the digital detox thing, or go "low-tech" you need to cut out digital services and social media first. Like, if you find yourself scrolling instagram reels every time you pick up the phone and suddenly it's been an hour and you had work to do, then yeah, go ahead and delete the app and logout on your browser for a while. If it's not easy to get to you can get over it quicker.
I get it. You feel like you waste too much time on whatever and that whatever is easily accessed on your phone. It's easy to change the device first to change your behavior. But once you've lost the constant urge to "check" stuff, you don't have to log back in. It's possible to have a smart phone that allows you to communicate with others without scrolling through the dopamine casino.
I think that in the next few years we will see a massive fall off of users on traditional social media sites. Twitter, Bluesky, Mastodon, Facebook, etc. Those that have the quick little updates that give you a stream of stuff to "check on". So much of it is just influencer ads or ai clickbait now anyway.
I watched it happen with blogs and forums. If all my internet usage is funneled into the Facebook/Youtube apps then why bother looking for answers to anything on a forum or blog? How do I change the oil in a mini cooper? Youtube will show me in 10 minutes or less. A forum will have a wall of dead photobucket links and no explanation.
But, going back to the point here, if you have day to day tasks that require you to use your phone (and modern apps) for work/banking/transportation then you are going to have a terrible time trying to do so by changing the device before changing your habits. Delete the app, log out of the account, keep your ability to use maps and Venmo.
Back when we used real flip phones they still had paper maps and payphones at the gas station. There was a guy sitting in a booth at the parking lot to take your money. We wrote checks at the grocery store. McDonalds was cash only until I was in college.
Day to day technology has advanced, it's ok to use it and still be low tech. I watch shows and listen to music on physical media. I use Zunes and iPods and tape players and vintage consoles and all that. But I don't want to be the person who exists in a modern world who refuses to use modern tech just because I can't stop scrolling instagram reels. I don't mind inconveniencing myself with the way I use tech, but I certainly don't want to be a burden to others because of it.