Black screen after plugging external monitor, works if plugged before boot

Hello, I installed Fedora 34 on my Acer Swift 1 SF114-32, today I tried to plug an external monitor into the built-in HDMI port: suddently both the laptop and external monitor screens went black, as they received a totally black signal from VGA. The only way to recover from this status is to hard reset the laptop with the standard power on button; however if I plug the monitor before booting the system everything works perfectly.
I’m running latest kernel version 5.11.19 but even with 5.9.0 this problem persists, I also tried with both Wayland and X.org Sessions of Gnome and this didn’t make any difference.
These are last lines of system log before the hard reset:

Riepilogo
mag 15 00:40:14 swift1 audit[1]: SERVICE_START pid=1 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:init_t:s0 msg='unit=systemd-tmpfiles-clean comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'
mag 15 00:40:14 swift1 audit[1]: SERVICE_STOP pid=1 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:init_t:s0 msg='unit=systemd-tmpfiles-clean comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'
mag 15 00:40:15 swift1 rtkit-daemon[687]: Supervising 14 threads of 8 processes of 2 users.
mag 15 00:40:15 swift1 rtkit-daemon[687]: Supervising 14 threads of 8 processes of 2 users.
mag 15 00:40:30 swift1 rtkit-daemon[687]: Supervising 14 threads of 8 processes of 2 users.
mag 15 00:40:30 swift1 rtkit-daemon[687]: Supervising 14 threads of 8 processes of 2 users.
mag 15 00:41:57 swift1 wpa_supplicant[936]: wlp0s12f0: WPA: Group rekeying completed with 12:13:31:55:75:eb [GTK=TKIP]
mag 15 00:45:08 swift1 systemd[1]: fwupd.service: Deactivated successfully.
mag 15 00:45:08 swift1 audit[1]: SERVICE_STOP pid=1 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:init_t:s0 msg='unit=fwupd comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'
mag 15 00:45:12 swift1 polkitd[778]: Registered Authentication Agent for unix-process:3986:123970 (system bus name :1.169 [flatpak list], object path /org/freedesktop/PolicyKit1/AuthenticationAgent, locale C)
mag 15 00:45:12 swift1 polkitd[778]: Unregistered Authentication Agent for unix-process:3986:123970 (system bus name :1.169, object path /org/freedesktop/PolicyKit1/AuthenticationAgent, locale C)
mag 15 00:46:12 swift1 wpa_supplicant[936]: wlp0s12f0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-66 noise=9999 txrate=585000
mag 15 00:46:14 swift1 rtkit-daemon[687]: Supervising 14 threads of 8 processes of 2 users.
mag 15 00:46:14 swift1 rtkit-daemon[687]: Supervising 14 threads of 8 processes of 2 users.
mag 15 00:47:03 swift1 firefox.desktop[3861]: libva info: VA-API version 1.11.0
mag 15 00:47:03 swift1 firefox.desktop[3861]: libva info: Trying to open /usr/lib64/dri/iHD_drv_video.so
mag 15 00:47:03 swift1 firefox.desktop[3861]: libva info: Found init function __vaDriverInit_1_11
mag 15 00:47:03 swift1 firefox.desktop[3861]: libva info: va_openDriver() returns 0
mag 15 00:47:14 swift1 systemd[1]: Starting dnf makecache...
mag 15 00:47:14 swift1 dnf[4205]: Cache dei metadati aggiornata recentemente.
mag 15 00:47:14 swift1 systemd[1]: dnf-makecache.service: Deactivated successfully.
mag 15 00:47:14 swift1 systemd[1]: Finished dnf makecache.
mag 15 00:47:14 swift1 audit[1]: SERVICE_START pid=1 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:init_t:s0 msg='unit=dnf-makecache comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'
mag 15 00:47:14 swift1 audit[1]: SERVICE_STOP pid=1 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:init_t:s0 msg='unit=dnf-makecache comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'
mag 15 00:49:29 swift1 wpa_supplicant[936]: wlp0s12f0: CTRL-EVENT-SIGNAL-CHANGE above=0 signal=-66 noise=9999 txrate=175600
mag 15 00:50:06 swift1 wpa_supplicant[936]: wlp0s12f0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-67 noise=9999 txrate=175600
mag 15 00:51:25 swift1 rtkit-daemon[687]: Supervising 14 threads of 8 processes of 2 users.
mag 15 00:51:25 swift1 rtkit-daemon[687]: Supervising 14 threads of 8 processes of 2 users.
mag 15 00:51:57 swift1 wpa_supplicant[936]: wlp0s12f0: WPA: Group rekeying completed with 12:13:31:55:75:eb [GTK=TKIP]
mag 15 00:52:22 swift1 wpa_supplicant[936]: wlp0s12f0: CTRL-EVENT-SIGNAL-CHANGE above=0 signal=-67 noise=9999 txrate=234000
mag 15 00:53:27 swift1 wpa_supplicant[936]: wlp0s12f0: CTRL-EVENT-SIGNAL-CHANGE above=0 signal=-68 noise=9999 txrate=585000
mag 15 00:54:45 swift1 wpa_supplicant[936]: wlp0s12f0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-66 noise=9999 txrate=585000
mag 15 00:55:05 swift1 gnome-shell[1822]: libinput error: event5  - SYN1B7F:00 06CB:CD41 Touchpad: kernel bug: Touch jump detected and discarded.
mag 15 00:55:05 swift1 gnome-shell[1822]: See https://wayland.freedesktop.org/libinput/doc/1.17.2/touchpad-jumping-cursors.html for details
mag 15 00:55:06 swift1 gnome-keyring-daemon[1720]: asked to register item /org/freedesktop/secrets/collection/login/1, but it's already registered
mag 15 01:01:02 swift1 CROND[4470]: (root) CMD (run-parts /etc/cron.hourly)
mag 15 01:01:02 swift1 run-parts[4473]: (/etc/cron.hourly) starting 0anacron
mag 15 01:01:02 swift1 anacron[4483]: Anacron started on 2021-05-15
mag 15 01:01:02 swift1 anacron[4483]: Normal exit (0 jobs run)
mag 15 01:01:02 swift1 run-parts[4485]: (/etc/cron.hourly) finished 0anacron
mag 15 01:01:02 swift1 CROND[4469]: (root) CMDEND (run-parts /etc/cron.hourly)
mag 15 01:01:57 swift1 wpa_supplicant[936]: wlp0s12f0: WPA: Group rekeying completed with 12:13:31:55:75:eb [GTK=TKIP]
mag 15 01:03:48 swift1 wpa_supplicant[936]: wlp0s12f0: CTRL-EVENT-SIGNAL-CHANGE above=0 signal=-68 noise=9999 txrate=585000
mag 15 01:05:37 swift1 wpa_supplicant[936]: wlp0s12f0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-67 noise=9999 txrate=585000
mag 15 01:06:31 swift1 wpa_supplicant[936]: wlp0s12f0: CTRL-EVENT-SIGNAL-CHANGE above=0 signal=-65 noise=9999 txrate=585000

Any ideas about a solution for this issue?
Thank you all

What graphics card(s) does that machine have. If nvidia is one of them do you have the drivers installed for it?

Thank you for your answer, my laptop only has Intel integrated graphics card, more precisely from lshw output:

*-display
             description: VGA compatible controller
             product: GeminiLake [UHD Graphics 605]
             vendor: Intel Corporation
             physical id: 2
             bus info: pci@0000:00:02.0
             version: 03
             width: 64 bits
             clock: 33MHz
             capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
             configuration: driver=i915 latency=0
             resources: irq:126 memory:a0000000-a0ffffff memory:90000000-9fffffff ioport:1000(size=64) memory:c0000-dffff

If you start with the cable connected, have a look in the monitor settings if you can lower the frequency of the monitor and save it this way. In a other topic I saw this as solution.

I tried different resolution-frequency combinations but none of these made any difference; every time I select a second screen output both laptop and external monitor go blank (with a black input signal).