1、确认当前 Repository 已经切换为 Fedora 的官方源
2、依次执行
dnf upgrade --refresh -y
dnf install dnf-plugin-system-upgrade -y
dnf system-upgrade download --releasever=39 -y
dnf system-upgrade reboot

详细过程：

[root@fedora fedora]# cat /etc/yum.repos.d/fedora-modular.repo
[fedora-modular]
name=Fedora Modular $releasever - $basearch
baseurl=http://mirrors.aliyun.com/fedora/releases/$releasever/Modular/$basearch/os/

metalink=https://mirrors.fedoraproject.org/metalink?repo=fedora-modular-$releasever&arch=$basearch

enabled=1
countme=1
metadata_expire=7d
repo_gpgcheck=0
type=rpm
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-$releasever-$basearch
skip_if_unavailable=False
[fedora-modular-debuginfo]
name=Fedora Modular $releasever - $basearch - Debug
baseurl=http://mirrors.aliyun.com/fedora/releases/$releasever/Modular/$basearch/debug/tree/

metalink=https://mirrors.fedoraproject.org/metalink?repo=fedora-modular-debug-$releasever&arch=$basearch

enabled=0
metadata_expire=7d
repo_gpgcheck=0
type=rpm
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-$releasever-$basearch
skip_if_unavailable=False
[fedora-modular-source]
name=Fedora Modular $releasever - Source
baseurl=http://mirrors.aliyun.com/fedora/releases/$releasever/Modular/source/tree/

metalink=https://mirrors.fedoraproject.org/metalink?repo=fedora-modular-source-$releasever&arch=$basearch

enabled=0
metadata_expire=7d
repo_gpgcheck=0
type=rpm
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-$releasever-$basearch
skip_if_unavailable=False
[root@fedora fedora]#
[root@fedora fedora]# ls -F /etc/yum.repos.d/
_copr:copr.fedorainfracloud.org:phracek:PyCharm.repo fedora-modular.repo.original fedora-updates-modular.repo.original fedora-updates-testing-modular.repo.original rpmfusion-nonfree-nvidia-driver.repo
docker-ce.repo fedora.repo fedora-updates.repo fedora-updates-testing.repo rpmfusion-nonfree-steam.repo
fedora-cisco-openh264.repo fedora.repo.original fedora-updates.repo.original fedora-updates-testing.repo.original
fedora-modular.repo fedora-updates-modular.repo fedora-updates-testing-modular.repo google-chrome.repo
[root@fedora fedora]#
[root@fedora fedora]# mv /etc/yum.repos.d/fedora-modular.repo /etc/yum.repos.d/fedora-modular.repo.38.Aliyun
[root@fedora fedora]#
[root@fedora fedora]# cp /etc/yum.repos.d/fedora-modular.repo.original /etc/yum.repos.d/fedora-modular.repo
[root@fedora fedora]#
[root@fedora fedora]# cat /etc/yum.repos.d/fedora-modular.repo
[fedora-modular]
name=Fedora Modular $releasever - $basearch

baseurl=http://download.example/pub/fedora/linux/releases/$releasever/Modular/$basearch/os/

metalink=https://mirrors.fedoraproject.org/metalink?repo=fedora-modular-$releasever&arch=$basearch
enabled=1
countme=1
metadata_expire=7d
repo_gpgcheck=0
type=rpm
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-$releasever-$basearch
skip_if_unavailable=False
[fedora-modular-debuginfo]
name=Fedora Modular $releasever - $basearch - Debug

baseurl=http://download.example/pub/fedora/linux/releases/$releasever/Modular/$basearch/debug/tree/

metalink=https://mirrors.fedoraproject.org/metalink?repo=fedora-modular-debug-$releasever&arch=$basearch
enabled=0
metadata_expire=7d
repo_gpgcheck=0
type=rpm
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-$releasever-$basearch
skip_if_unavailable=False
[fedora-modular-source]
name=Fedora Modular $releasever - Source

baseurl=http://download.example/pub/fedora/linux/releases/$releasever/Modular/source/tree/

metalink=https://mirrors.fedoraproject.org/metalink?repo=fedora-modular-source-$releasever&arch=$basearch
enabled=0
metadata_expire=7d
repo_gpgcheck=0
type=rpm
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-$releasever-$basearch
skip_if_unavailable=False
[root@fedora fedora]#
[root@fedora fedora]# dnf upgrade --refresh -y
Copr repo for PyCharm owned by phracek 1.3 kB/s | 2.1 kB 00:01
Docker CE Stable - x86_64 11 kB/s | 3.5 kB 00:00
Fedora 38 - x86_64 27 kB/s | 6.1 kB 00:00
Fedora 38 openh264 (From Cisco) - x86_64 559 B/s | 989 B 00:01
Fedora Modular 38 - x86_64 162 kB/s | 177 kB 00:01
Fedora 38 - x86_64 - Updates 42 kB/s | 8.1 kB 00:00
Fedora Modular 38 - x86_64 - Updates 28 kB/s | 4.9 kB 00:00
google-chrome 4.2 kB/s | 1.3 kB 00:00
RPM Fusion for Fedora 38 - Nonfree - NVIDIA Driver 11 kB/s | 15 kB 00:01
RPM Fusion for Fedora 38 - Nonfree - Steam 12 kB/s | 14 kB 00:01
Dependencies resolved.
Nothing to do.
Complete!
[root@fedora fedora]#
[root@fedora fedora]# dnf install dnf-plugin-system-upgrade -y
Last metadata expiration check: 0:00:17 ago on Sat 18 Nov 2023 12:25:10 PM CST.
Package dnf-plugins-core-4.4.3-1.fc38.noarch is already installed.
Dependencies resolved.
Nothing to do.
Complete!
[root@fedora fedora]#
[root@fedora fedora]# dnf system-upgrade download --releasever=39 -y
Copr repo for PyCharm owned by phracek 2.2 kB/s | 2.1 kB 00:00
Docker CE Stable - x86_64 8.6 kB/s | 3.5 kB 00:00
Fedora 39 - x86_64 34 kB/s | 6.1 kB 00:00
Fedora 39 openh264 (From Cisco) - x86_64 902 B/s | 989 B 00:01
Fedora Modular 39 - x86_64 519 kB/s | 1.7 MB 00:03
Fedora 39 - x86_64 - Updates 3.3 MB/s | 14 MB 00:04
Fedora Modular 39 - x86_64 - Updates 452 B/s | 257 B 00:00
google-chrome 4.1 kB/s | 3.6 kB 00:00
RPM Fusion for Fedora 39 - Nonfree - NVIDIA Driver 8.0 kB/s | 14 kB 00:01
RPM Fusion for Fedora 39 - Nonfree - Steam 1.4 kB/s | 2.2 kB 00:01

Dependencies resolved.

Package Architecture Version Repository Size

Installing:
kernel x86_64 6.5.11-300.fc39 updates 148 k
kernel-core x86_64 6.5.11-300.fc39 updates 16 M
kernel-modules x86_64 6.5.11-300.fc39 updates 57 M
kernel-modules-core x86_64 6.5.11-300.fc39 updates 31 M
kernel-modules-extra x86_64 6.5.11-300.fc39 updates 2.6 M
Upgrading:
Box2D x86_64 2.4.1-11.fc39 fedora 106 k
ImageMagick x86_64 1:7.1.1.15-1.fc39 fedora 82 k
ImageMagick-libs x86_64 1:7.1.1.15-1.fc39 fedora 2.5 M
LibRaw x86_64 0.21.1-5.fc39 fedora 417 k
ModemManager x86_64 1.20.6-3.fc39 fedora 1.2 M
ModemManager-glib x86_64 1.20.6-3.fc39 fedora 326 k
NetworkManager x86_64 1:1.44.2-1.fc39 updates 2.2 M
NetworkManager-adsl x86_64 1:1.44.2-1.fc39 updates 27 k
NetworkManager-bluetooth x86_64 1:1.44.2-1.fc39 updates 53 k
NetworkManager-config-connectivity-fedora noarch 1:1.44.2-1.fc39 updates 13 k
NetworkManager-libnm x86_64 1:1.44.2-1.fc39 updates 1.8 M
NetworkManager-openconnect x86_64 1.2.10-2.fc39 fedora 581 k
NetworkManager-openconnect-gnome x86_64 1.2.10-2.fc39 fedora 46 k
NetworkManager-openvpn x86_64 1:1.10.2-3.fc39 fedora 292 k
NetworkManager-openvpn-gnome x86_64 1:1.10.2-3.fc39 fedora 71 k
NetworkManager-ppp x86_64 1:1.44.2-1.fc39 updates 36 k
NetworkManager-pptp x86_64 1:1.2.12-3.fc39 fedora 143 k
NetworkManager-pptp-gnome x86_64 1:1.2.12-3.fc39 fedora 41 k
NetworkManager-team x86_64 1:1.44.2-1.fc39 updates 32 k
NetworkManager-vpnc x86_64 1:1.2.8-4.fc39 fedora 180 k
NetworkManager-vpnc-gnome x86_64 1:1.2.8-4.fc39 fedora 38 k
NetworkManager-wifi x86_64 1:1.44.2-1.fc39 updates 133 k
NetworkManager-wwan x86_64 1:1.44.2-1.fc39 updates 59 k
Upgrading Environment Groups:
Fedora Workstation
Upgrading Groups:
Anaconda tools
base-x
Container Management
Core
Firefox Web Browser
Fonts
GNOME
Guest Desktop Agents
Hardware Support
LibreOffice
Multimedia
Common NetworkManager Submodules
Printing Support
Fedora Workstation product core

Transaction Summary

Install 134 Packages
Upgrade 1943 Packages
Remove 5 Packages
Downgrade 9 Packages
Total download size: 1.9 G

DNF will only download packages, install gpg keys, and check the transaction.

Total 3.9 MB/s | 1.9 GB 08:19
Fedora 39 - x86_64 1.6 MB/s | 1.6 kB 00:00
Importing GPG key 0x18B8E74C:
Userid : "Fedora (39) "
Fingerprint: E8F2 3996 F232 1864 0CB4 4CBE 75CF 5AC4 18B8 E74C
From : /etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-39-x86_64
Key imported successfully
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Complete!
Transaction saved to /var/lib/dnf/system-upgrade/system-upgrade-transaction.json.
Download complete! Use 'dnf system-upgrade reboot' to start the upgrade.
To remove cached metadata and transaction use 'dnf system-upgrade clean'
The downloaded packages were saved in cache until the next successful transaction.
You can remove cached packages by executing 'dnf clean packages'.
[root@fedora fedora]#
[root@fedora fedora]# dnf system-upgrade reboot