Why won't Boxes work?

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Hi there. This is my first question. I'm quite new to Fedora, but have been using Ubuntu for a long time. On Ubuntu, when I couldn't get Boxes to work, I needed to sudo adduser USERNAME kvm, while I assume that's the issue I'm facing now, I have no idea how to do it on Fedora.

This is what comes up in the troubleshooting information:

Broker URL: qemu+unix:///session
Domain: boxes-unknown
UUID: 519b9889-6ff2-4568-a782-1f50ed825bb7
Persistent: yes
Cpu time: 0
Memory: 8402189 KiB
Max memory: 16331744 KiB
CPUs: 8
State: GVIR_DOMAIN_STATE_SHUTOFF

Domain config:
------------------------------------------------------------
<domain type="kvm">
  <name>boxes-unknown</name>
  <uuid>519b9889-6ff2-4568-a782-1f50ed825bb7</uuid>
  <title>tails-amd64-3</title>
  <metadata>
    <boxes:gnome-boxes xmlns:boxes="https://wiki.gnome.org/Apps/Boxes">
      <os-state>live</os-state>
      <media>/nfs/linuxisos/Tails/tails-amd64-3.9.iso</media>
    </boxes:gnome-boxes>
  </metadata>
  <memory unit="KiB">8402189</memory>
  <currentMemory unit="KiB">8402189</currentMemory>
  <vcpu placement="static">8</vcpu>
  <os>
    <type arch="x86_64" machine="pc-i440fx-3.0">hvm</type>
    <boot dev="cdrom"/>
    <boot dev="hd"/>
  </os>
  <features>
    <acpi/>
    <apic/>
  </features>
  <cpu mode="custom" match="exact" check="partial">
    <model fallback="allow">Haswell-noTSX-IBRS</model>
    <topology sockets="1" cores="4" threads="2"/>
  </cpu>
  <clock offset="utc">
    <timer name="rtc" tickpolicy="catchup"/>
    <timer name="pit" tickpolicy="delay"/>
    <timer name="hpet" present="no"/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>destroy</on_reboot>
  <on_crash>destroy</on_crash>
  <pm>
    <suspend-to-mem enabled="no"/>
    <suspend-to-disk enabled="no"/>
  </pm>
  <devices>
    <emulator>/usr/bin/qemu-kvm</emulator>
    <disk type="file" device="disk">
      <driver name="qemu" type="qcow2" cache="writeback"/>
      <source file="/home/username/.local/share/gnome-boxes/images/boxes-unknown"/>
      <target dev="hda" bus="ide"/>
      <address type="drive" controller="0" bus="0" target="0" unit="0"/>
    </disk>
    <disk type="file" device="cdrom">
      <driver name="qemu" type="raw"/>
      <source file="/nfs/linuxisos/Tails/tails-amd64-3.9.iso" startupPolicy="mandatory"/>
      <target dev="hdc" bus="ide"/>
      <readonly/>
      <address type="drive" controller="0" bus="1" target="0" unit="0"/>
    </disk>
    <controller type="usb" index="0" model="ich9-ehci1">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x05" function="0x7"/>
    </controller>
    <controller type="usb" index="0" model="ich9-uhci1">
      <master startport="0"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x05" function="0x0" multifunction="on"/>
    </controller>
    <controller type="usb" index="0" model="ich9-uhci2">
      <master startport="2"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x05" function="0x1"/>
    </controller>
    <controller type="usb" index="0" model="ich9-uhci3">
      <master startport="4"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x05" function="0x2"/>
    </controller>
    <controller type="pci" index="0" model="pci-root"/>
    <controller type="ide" index="0">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x01" function="0x1"/>
    </controller>
    <controller type="virtio-serial" index="0">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x06" function="0x0"/>
    </controller>
    <controller type="ccid" index="0">
      <address type="usb" bus="0" port="2"/>
    </controller>
    <interface ...