Fair enough, I probably wrote most people just as an automatic phrase when it should be "some people"

This is more like "just increase friction". For some people it's more than enough, for others it's barely anything. Personally speaking, I've found that just the act of removing the reddit app from my home screen makes it fairly less likely to be opened, as now I need to open my app drawer.

Check my math here, but 1 is larger than 0.

I do not, the gym phone has its own SIM. I have it running a cheap data-only eSIM from esimdb.com

If you need synchronized phone / text messages, I suggest Google Voice. When anyone rings your (free) Google Voice number, it will forward the call to multiple phone numbers. It will ring as a regular phone call, not as an app notification. However, text messages appear as app notifications.

Apparently some phone companies can/will provide you with aux SIMs, which allows two phone to share a number, or so I've been lead to believe. I can't find a single provider here in Denmark that will issue me such a SIM. Kinda sad about that, because it would solve most of my issues.

I need a smartphone for a few things every so often, but most of the time a dumb phone is perfectly fine.

What do you think of the minimal phone? https://minimalcompany.com/

Large pile of waffle incoming:

This was the way for me. I spent a good few years trying proper dumbphones, but I always needed an app for something. Carrying two phones didn't work, no off the shelf 'Smart, yet dumb' phone had the particular mix of features I needed.

The best half way house I found was a Nokia 2720, it runs Kai OS (Formerly Firefox OS), so very easy to throw a quick app together and add new features as needed. Unfortunately all the important apps were similarly thrown together, battery life was awful, calls, alarms and messages came through when they felt like it, the T9 predictive text was diabolically bad.

I went back to basic android for a while, tried all sorts of settings and methods to cut back, but I am just too vulnerable to their flashy attention grabbing tricks.

But the e-ink? Hot damn it worked. Everything I actually needed, and just enough friction that I don't use any more. The lack of colour certainly neutralises a lot of the attention grabbing tactics, but I think the real difference for me is the lack of fluidity. It's always just a device, and never reaches extension of self territory. It is truly refreshing how many times I've left the house without it and only noticed a few hours later.

As for manufacturers and quality, I went with a Hisense A9 as it seemed to have the best open source support at the time. It was a bit pricey considering the general specs, but when the screen is the bottleneck you don't miss the processor speed or camera quality. (I actually quite like the lousy photo experience, it feels a bit more like film, or early digital where you just have to shoot and hope it comes out ok)

Despite that, I've ended up sticking with the manufacturer ROM with just a few tweaks. Perhaps its selling all my data to the CCP, but it's rock solid and much more polished than any cheap android phone I've used previously. It's really well set up to get the best from the hardware too, in a way that the lineage port couldn't quite match.

If you think it might work for you, I'd definitely recommend giving it a try.

The main caveat I'd offer if you're trying to reduce your screen time is that it doesn't work if you primarily waste time reading. Reading is a joy with this, and I am much more likely than before to pick up an e-book or finish a long article I'd otherwise have skimmed.

Other quirks of the A9 if anyone is considering it: - The GNSS receiver is atrocious, it regularly fails to get a fix in clear open fields. - It's a small battery, low power phone. I usually get most of a week out of a charge, but one heavy background app can drop that to less than a day. Discord was the worst until stopping all background activity, WiFi hotspot is also pretty brutal on the battery. - The stock OS has a deliberately very limited notification system. Get used to intentionally checking for messages every now and then - Doesn't play nice with non-chinese carriers. Out of the box I had intermittent SMS, no VoLTE and regular call drops. All fixable via shuffling some files around over ADB though, see XDA for the how to - All specs are OK. The camera is OK. The speakers are OK. The processor processes. That's all you get. - Some apps are just not E-Ink friendly. Spotify and google maps are the worst I use regularly. Scrolling, full screen movement, contrast and dark themes are the enemy. They are both totally useable, but it can take more than a glance. - No IP rating, I don't go swimming with it but it sure rains a lot here and I don't like having to care + The 3.5mm output is gorgeous, sounds fantastic with any headphones I've tried. Easily the best of any smartphone I've used + It is very nice E-Ink. Lots of totally useable apps for the A9 would not be so on a lesser screen. + Though I rarely use it, the frontlight is very nice to have and intuitively controlled

> customer retention

I suppose you're referring to engagement maximization algorithms (my words) of socials?

> already deep in their hands

If a person observes they're sensitive to these, do they really need an additional device to disrupt their reactive behavior and be a little bit more deliberate in what they do?

> remove or limit their products

Is deleting the apps or using them in moderation[1] really so hard?

[1] One form of moderation I've found is to disable notifications for those (if not all) apps. Again, seizing control instead of being reactive to whatever some platform/app/device decides to shove down your throat at any given time.

You're saying DumbPhone is a potential mainstream product?

Why would that be bad?