There are services I need like banking and pensions and tax which would be more challenging to manage without any online presence, but that doesn't necessarily require a phone. But sometimes, of course, it's just really convenient if you can't be at your laptop - everyone knows a phone can be a camera, a map, a weather forecaster, a 'whatever-you-want'. It's the conduit for messages from my family, who all use instant messaging apps to stay in touch. It's just important to make sure that it doesn't also become a distraction, to ensure I don't habitually reach for it whenever a thought occurs to me and I want to look something up, or worst of all when I'm bored and want to fill some time.
I bought my first mobile phone in 1993 or '94. It was a Sony CM-H333, known as the 'Mars Bar' phone, and I have a feeling it cost almost £500 [1]. It had an antenna which you pulled out of the body, it was analogue rather than digital so people with a radio scanner could listen to your conversations, and the nickel-cadmium battery didn't last long. All it did was make and receive calls, because as I recall it didn't support text messages, but that was fine. I didn't make or receive many calls, which were expensive and the £25 per month airtime subscription only included 15 minutes for free (how times change - today I get unlimited talk time and texts for £4 a month). There were occasions when it was invaluable, like the time I got stuck in Calais, waiting for a ferry back from France which had broken down, and I needed to let someone at home know I'd be late. Very late. And the phone connected to the UK network across 22 miles of the English Channel without a problem (no international roaming back then).
Phone calls are still the best reason for having one at all. A few months ago I had to renew my home broadband and phone package and I decided a landline was an unecessary additional cost I could manage without, so now I only have a mobile number. A landline replacement doesn't need to be a smartphone, and what I carry around in my pocket is a Punkt MP2 [2]. It makes and receives calls and SMS texts, it has one or two other basic features but no camera and there are no apps to install, except a messaging feature which uses Signal, although I don't have that. So in terms of essential functionality it's not so very different to that old CM-H333.
What it _does_ have is a wi-fi hotspot which I can switch on when I need it. That means I can have my smartphone with me, not connected to a network or it can even be switched off and put in my bag until I actually need it. Then I turn on the wi-fi on the Punkt, tether the smartphone to it for as long as it takes to do whatever I need to do, then switch it off again. It only takes a small amount of time to turn the internet on and connect, but it isn't _zero_ time and that's enough of an obstacle to make me use the technology more mindfully.
I also have a low-spec Android phone, and it has the Minimalist Phone launcher [3] installed on it. This replaces the normal Android home screens covered in colourful icons with a simple list of apps in white text on a black background. The launcher also allows me to set a delay for opening apps and a usage time limit for things I want to use less or more mindfully, and this introduces another barrier to casual web browsing. It takes a couple of minutes to switch these limits off, and I've found that very little casual use is important enough to wait that long, especially added to the time it takes to switch on the MP2 hotspot and tether the smartphone to it.
I can resist anything except tempation - Oscar Wilde, Lady Windermere's Fan
These measures may seem to indicate that I have no willpower whatsoever, and that may be true. I haven't been on any kind of social media for a number of years, and that has been a huge part of the solution too, and switching devices off when I'm at home and putting them away in a drawer or cupboard has also helped.
This combined approach works very well. Most of the things that I used to do reflexively when they popped into my mind, pulling the smartphone out of my back pocket to look something up, often turn out not to be very important: they can usually wait until I can deal with them on the computer. I carry a Moleskine weekly notebook, which has each week's diary on the left page and a ruled page for notes on the right, so I can write down reminders, questions that I need to research, shopping lists, whatever. Anything that I might once have used the phone to deal with immediately can just be written on paper and actioned later.
This won't work for everyone. The Punkt MP2 isn't cheap, but if you want a non-smart phone with a wi-fi hotspot there aren't a huge number of alternatives. I like it though, and it's comforting to know that I'm contactable if necessary (which is very rare) but I can also be more in control, using the technology rather than feeling like I'm being used by it.
[1] https://www.mobilephonemuseum.com/phone-detail/sony-cm-h333
[2] https://www.punkt.ch/products/mp02-4g-minimalist-phone
[3] https://www.minimalistphone.com/
Email: kdan01 [at] posteo [dot] net