No IPv4 connectivity on cellular network

/e/ version: 2020051454221
Device model: Galaxy S8, SM-G950F
When it started to occur: ?
Reproducible with the last /e/ version: yes
Reproducible with LineageOS: ?

Summary

I'm not sure if this is an issue with /e/ OS, the device, or the mobile network. If the device is only connected to the cellular network (Deutsche Telekom), the device gets an IPv4 and an IPv6 address but is only able to communicate via IPv6. Servers without IPv6 address are not reachable. I cannot tell when this started because I used this device (got it just some days ago) because of the Corona restrictions only at home with WiFi until yesterday. However, another phone on the same cellular network works fine.

The device is unusable
The bug is the source of a data loss or a big waste of time
The bug concerns a third party app
The bug concerns security
The bug concerns privacy

The problem

Steps to reproduce

Turn of WiFi, try to open a website that is IPv4-only in the browser app, for example duckduckgo.com.

What is the current behavior?

The site cannot be reached (ERR_NAME_NOT_RESOLVED).

What is the expected correct behavior?

The site opens.

Technical information

IP info

dreamlte:/ $ ip addr
<snip>
3: rmnet0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc mq state UNKNOWN group default qlen 1000
    link/ppp 
    inet 10.47.88.86/24 scope global rmnet0
       valid_lft forever preferred_lft forever
    inet6 2a01:<snip>/64 scope global 
       valid_lft forever preferred_lft forever
    inet6 fe80::<snip>/64 scope link 
       valid_lft forever preferred_lft forever
<snip>
dreamlte:/ $ ping -c1 google.de
connect: Network is unreachable
2|dreamlte:/ $ ping6 -c1 google.de                                             
PING google.de(muc11s01-in-x03.1e100.net) 56 data bytes
64 bytes from muc11s01-in-x03.1e100.net: icmp_seq=1 ttl=50 time=64.5 ms

--- google.de ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 64.508/64.508/64.508/0.000 ms

Relevant screenshots

No screenshots.

Solutions

Workaround

No workaround.

Possible fixes

No possible fixes.