For national wide firewalls in some countries, just black-listed sites are blocked, such as github or youtube. Proxy servers always have limited bandwidth and they are only used for blocked sites.
Some companies, have also blocked github to prevent employee copying & pasting code from open-source projects.
System level proxy is usually not a good idea because it will decrease the speed of normal accessible sites. So I will never setup a system-wide proxy. But I am using a plugin named SwitchySharp in Chrome, it allows me initialize some rules to indicate which site need the proxy and which site can use direct link.
Github is indeed blocked in some countries, which will affect Obsidian’s plugin & theme installation experience.
I’m waiting for an update as well (waiting for socks5 support with username and password). It seemes to me that the developer of Obsidian do not know/understand how a company network and internet access in a (big) company works. Or they understand it and do not want companies as customer. In the latter case a clear statement would be helpfull. In the actual situation we cannot buy more licenses and cannot roll it out for a larger user base.