Error: could not find a distribution template for Sparky/bullseye

[KlemensPL]

Hi!
I was trying to use

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sudo apt-add-repository non-free, but I get error

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raise NoDistroTemplateException(
aptsources.distro.NoDistroTemplateException: Error: could not find a distribution template for Sparky/bullseye
During research I found out that it's common error, but by the fixing it it's possible to harm the OS and could dependence on distribution. Thus, I decide to put the topic here. Do you know how to safely fix it to use 'non-free' for Sparky?
Thanks in advance!

Full terminal operations code:

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sudo apt-add-repository non-free
Traceback (most recent call last):
  File "/usr/bin/apt-add-repository", line 95, in <module>
    sp = SoftwareProperties(options=options)
  File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 109, in __init__
    self.reload_sourceslist()
  File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 599, in reload_sourceslist
    self.distro.get_sources(self.sourceslist)   
  File "/usr/lib/python3/dist-packages/aptsources/distro.py", line 91, in get_sources
    raise NoDistroTemplateException(
aptsources.distro.NoDistroTemplateException: Error: could not find a distribution template for Sparky/bullseye

cat /etc/os-release

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PRETTY_NAME="SparkyLinux 6.3 (Po-Tolo)"
NAME="SparkyLinux"
VERSION_ID="6.3"
VERSION="6.3 (Po-Tolo)"
ID=sparky
ID_LIKE=debian
HOME_URL="https://sparkylinux.org/"
SUPPORT_URL="https://sparkylinux.org/forum/"
BUG_REPORT_URL="https://sourceforge.net/p/sparkylinux/tickets"


[pavroo]

You don't need to add non-free repos to sparky, already done as default.

But there is an issue as you found, not solved yet.