It’s what I respond with when someone who doesn’t understand MC is trying to disable auth for no good reason, because they tend to be pirates. (people that say “unofficial launcher” tend to be people using something like tlauncher, which promotes piracy, and also breaks some network configs in the process)
Offline isn’t a fix for that error, so if this fix doesn’t work, then it’s something on your friend’s end with how they’re authenticating their microsoft account.
https://discourse.cubecoders.com/t/forge-frequently-asked-questions/2982#p-6411-im-getting-the-error-failed-to-verify-username-7
For “unable to connect server”, you can try your VPS’s IP instead of the domain Hostinger gave you, since they have some weird issues with their DNS records in some areas.