Description of problem:
My computer has a link-local IPv6 address, but it only has IPv4 access to the internet. It seems that domain names are sometimes resolved to IPv6 addresses instead of IPv4 adresses. In such cases, commands like dnf and flatpak fail and complain that the network is unreachable.

Version-Release number of selected component (if applicable):
systemd 248 (v248~rc4-1.fc34)

How reproducible:
Run "dnf --refresh upgrade" or "flatpak install XX" on an updated Fedora 34 installation. Sometimes it works, sometimes it fails because it cannot reach the network.

Steps to Reproduce:
1. Connect the computer to a router that supports IPv6 but the connection to the internet provider is IPv4 only.
2. Install Fedora 34 (I used Fedora-Workstation-Live-x86_64-34-20210317.n.0.iso)
3. Install updates (sudo dnf --refresh upgrade).
4. After a reboot, try running "sudo dnf --refresh upgrade" again. If it succeeds, try again in a few minutes until it fails.

Actual results:
"sudo dnf --refresh upgrade" fails with messages like this one:
Errors during downloading metadata for repository 'fedora-modular':
  - Curl error (7): Couldn't connect to server for https://mirrors.fedoraproject.org/metalink?repo=fedora-modular-34&arch=x86_64 []
Error: Failed to download metadata for repo 'fedora-modular': Cannot prepare internal mirrorlist: Curl error (7): Couldn't connect to server for https://mirrors.fedoraproject.org/metalink?repo=fedora-modular-34&arch=x86_64 []

At the same time, "ping mirrors.fedoraproject.org" returns "Network is unreachable", and I also could not access https://mirrors.fedoraproject.org from Firefox.

Expected results:
DNF and flatpak successfully download repository information and/or packages.

Additional info:
When "dnf --refresh upgrade" is failing, dig outputs:
[david@pc4 ~]$ dig mirrors.fedoraproject.org

; <<>> DiG 9.16.11-RedHat-9.16.11-5.fc34 <<>> mirrors.fedoraproject.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 65515
;; flags: qr rd ra; QUERY: 1, ANSWER: 11, AUTHORITY: 6, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;mirrors.fedoraproject.org.	IN	A

;; ANSWER SECTION:
mirrors.fedoraproject.org. 48	IN	CNAME	wildcard.fedoraproject.org.
wildcard.fedoraproject.org. 48	IN	A	209.132.190.2
wildcard.fedoraproject.org. 48	IN	A	152.19.134.142
wildcard.fedoraproject.org. 48	IN	A	38.145.60.21
wildcard.fedoraproject.org. 48	IN	A	152.19.134.198
wildcard.fedoraproject.org. 48	IN	A	8.43.85.67
wildcard.fedoraproject.org. 48	IN	A	38.145.60.20
wildcard.fedoraproject.org. 48	IN	A	8.43.85.73
wildcard.fedoraproject.org. 48	IN	A	67.219.144.68
wildcard.fedoraproject.org. 48	IN	A	140.211.169.196
wildcard.fedoraproject.org. 48	IN	A	140.211.169.206

;; AUTHORITY SECTION:
wildcard.fedoraproject.org. 48	IN	AAAA	2605:bc80:3010:600:dead:beef:cafe:fed9
wildcard.fedoraproject.org. 48	IN	AAAA	2610:28:3090:3001:dead:beef:cafe:fed3
wildcard.fedoraproject.org. 48	IN	AAAA	2620:52:3:1:dead:beef:cafe:fed6
wildcard.fedoraproject.org. 48	IN	AAAA	2605:bc80:3010:600:dead:beef:cafe:feda
wildcard.fedoraproject.org. 48	IN	AAAA	2604:1580:fe00:0:dead:beef:cafe:fed1
wildcard.fedoraproject.org. 48	IN	AAAA	2620:52:3:1:dead:beef:cafe:fed7

;; Query time: 0 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Thu Mar 18 21:47:48 EDT 2021
;; MSG SIZE  rcvd: 405

When I run "curl --verbose https://mirrors.fedoraproject.org/metalink?repo=fedora-modular-34&arch=x86_64", it seems to try those IPv6 addresses and fails with "Network is unreachable" because my internet connection is IPv4.

But sometimes everything works just fine. That happens when the output of the dig command does not contain the authoritative section with AAAA records. In such case, dnf works without any problem and the output of dig is:
[david@pc4 ~]$ dig mirrors.fedoraproject.org A

; <<>> DiG 9.16.11-RedHat-9.16.11-5.fc34 <<>> mirrors.fedoraproject.org A
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29222
;; flags: qr rd ra; QUERY: 1, ANSWER: 11, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;mirrors.fedoraproject.org.	IN	A

;; ANSWER SECTION:
mirrors.fedoraproject.org. 221	IN	CNAME	wildcard.fedoraproject.org.
wildcard.fedoraproject.org. 60	IN	A	38.145.60.21
wildcard.fedoraproject.org. 60	IN	A	152.19.134.142
wildcard.fedoraproject.org. 60	IN	A	209.132.190.2
wildcard.fedoraproject.org. 60	IN	A	8.43.85.73
wildcard.fedoraproject.org. 60	IN	A	8.43.85.67
wildcard.fedoraproject.org. 60	IN	A	140.211.169.196
wildcard.fedoraproject.org. 60	IN	A	140.211.169.206
wildcard.fedoraproject.org. 60	IN	A	67.219.144.68
wildcard.fedoraproject.org. 60	IN	A	38.145.60.20
wildcard.fedoraproject.org. 60	IN	A	152.19.134.198

;; Query time: 29 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Thu Mar 18 21:53:51 EDT 2021
;; MSG SIZE  rcvd: 237