1) you buy a piece of hardware (printer, cctv cameras etc.) that can only be set up with a phone or you have to work harder to find the web interface.
2) Banks - banks really suck.
3) Companies I work for who use VPNs where you need a SMS or authenticator, however this is usually easy to get around with a web authenticator and some companies have let me use a YubiKey instead which is actually much less hassle.
4) Car parking meters where they discriminate - I tend to avoid these ones.
5) QR code restaurant menus - hate these but usually can get around it by just asking somebody for a paper menu.
6) Phasing out of 3G causing low reception - this is annoying because there are fewer good dumbphones that have 4G modems. Also I hate Android and Android based phones which come with facebook app and social media stuff installed so I'm a bit more limited in options. However, I managed to get an Alcatel flip phone which has 4G and it's a bit buggy but reception is now good.
I'm surprised that I'm able to get by, given the enormous pressure everyone is put under to use a smart phone, but it gives me hope that it hasn't worked and you can still get by in society without them. It would be pretty terrible if everyone HAD to agree to a google or Apple EULA just to be a functioning citizen.