403 error on sudo apt-get update

Solution 1:

It sounds like you have a problem where the Ethernet network is configured to be restrictive, filtering all your traffic and disallowing traffic to destinations that are not permitted.

This means either a web proxy is in play, or the Ethernet network is restricted.

UNFORTUNATELY, as you state in response to my inquiry via comments, this is a workplace network you are talking about, so you can't just go plugging things into your corporate network and expect things to work. (Proper) Workplace network security doesn't work that way, and the wifi is likely connected to a guest network segregated from corporate stuff versus the corporate ethernet which has a lot more control of what it can or can't access (such as going to the Internet, and therefore putting instant 403 restrictions as your device is not allowed out; the concept of Bring Your Own Devices lends itself to having a wifi network that is segregated from Corporate items so you can't access corporate from wifi directly, instead having to traverse to the Internet to then reach back to things like work email, etc. via separate IPs and connections, and that similarly Corporate can't access devices on the wifi.).

The only solution here that will let you not violate corporate usage policies (and chances are there is an Acceptable Use Policy on your network) is to talk to your workplace IT team - those are the only people who can help because of the way business / corporate networks are built - the IT team and the Security Team at your employer hold the keys, so only they can help you.

(Chances are, though, they won't let a device they don't control onto the Ethernet network in a way that would work for you - this is typical IT Security policy at most businesses that have security teams.)