Providing/Submitting substitutes

[phodina]

Hi,

is there a way how to submit built packages to the official substitution server?

My point here is I wanted to install ungoogled-chromium-
96.0.4664.93-1 on my x86_64 machine and unfortunately it was not available [1]. 
Therefore I built it on more powerful machine and shared the outputs of the 
derivation.

However, since I already built the browser and it took several hours I'd like 
to provide it also to other people.

Is there a way to submit the outputs of derivation to the official substitution 
server or the only way would be to make public my substitution server?

I do understand that accepting the derivation outputs also involves trusting 
the other party. Correct me if I'm wrong but can't this be solved be verified 
by using guix challenge?
[1] http://ci.guix.gnu.org/search?query=ungoogled-chromium

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Petr