to make things easy for you , why not trying a supported provider usable with pbxepress.
Amazon, google, ovh......
Do you have Debian 10 VM available on provider.
I found a doc on 3CX.fr but this is related to DEB9 , are you interested by the link (it's in french)
Sorry, i'm not a linux guru to help you more advanced, but for sure it seems to me there's a mix (deb9 or deb 10) or a miss in 3cx docs about manual install on Deb10
Just wait advices from another guy more Linux experienced or 3CX Staff during the next weekThat's the whole point of this thread...
About monthly price, what do you get for 5€?
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