Mac computer running Ubuntu 18.04 disconnects from wifi when sleeping, causing problems using an Open VPN server.
My roommate got an old iMac all-in-one from a friend (said it was from around 2012 but I don't know how to check which model). When we got it, the drive was completely wiped and didn't have an OS, so we installed Ubuntu 18.04 and tried using it as a home network VPN server (for RDP and steam link purposes). I got everything to work and with a dynamic DNS service. I was able to connect to RDP from my university wifi with pretty good results. This worked even though the screen goes to sleep, so I figured the sleep mode doesn't cause any issues.
A few days later I tried connecting again to no avail. When I got home and checked the server I noticed that while everything was still running, it stopped recognizing the wifi and said it needed to be authenticated. It still remembered the password and just wanted me to hit enter (several times over because it prompted me repeatedly 20 or so times).
A Google search suggested that I need to turn off the power saving mode on the wifi card through iwconfig, which I did successfully and checked that everything was working. Unfortunately, two days later the same thing happened, power saving mode was still off, but the wifi needed to be authenticated with a password (several times) again...
Not sure where to go from here or what info is needed to solve the problem. Is it likely just a spotty driver? Would it be better to upgrade to a newer version of Ubuntu (I was nervous such old hardware would not be able to handle it)?
Can anyone suggest some troubleshooting tips so I can figure out what causes it to disconnect? I'm sure an ethernet connection would improve the situation, but all our ports are currently in use and I am hesitant to find a bigger switch or router at the moment.
