Could anyone go to barter.vg?

As the error code already states, the TLS certificate isn't signed by the authority. Wait until admin fixes that.

It appears the domain was not renewed and has been deleted. It might still be recoverable, but I don't know the exact rules of the .vg registry.
Whois entry, edited out irrelevant lines:
Domain Name: BARTER.VG
Updated Date: 2024-10-28T10:05:16.0Z <- it is where the delete command was issued
Registry Expiry Date: 2024-11-01T23:59:59.0Z <- this shows when the domain should normally expire, however it appears it has been deleted a few days earlier, which is not "normal", but typical to some registrars
Domain Status: pendingDelete <- this indicates that the domain has been deleted
Domain Status: redemptionPeriod <- this indicates that the domains might still be recoverable

The SSL error is just a side effect. The cert belongs to some entity called "traffic club", which might have an agreement with the registrar or the registry to monetise the deleted domains.

See here for a reply from Lilly: https://steamcommunity.com/groups/bartervg/discussions/1/4695658272798171875/#c4695658272798173965

Hello everyone, we're already aware of these issues.
Unfortunately the admin is the only one who can investigate / fix this, and since he's not around daily, this might take some time.
Thank you for your patience and understanding.