I don’t know how much time you have left, but if it’s a dedicated server machine/system (I assume it is since it’s running Ubuntu Server) you could look into installing Pterodactyl which is a game server panel + daemon which can take care of setting up and running game servers for you. It uses Docker under the hood which helps solve issues like this.
I see there is an egg for this game that someone has made for Pterodactyl (eggs are just basically instructions for Pterodactyl on how to create a game server) that you could import, and then just practically hit create. This particular one uses Ubuntu 16.04 as a container image, which would make sense if that game needs libssl 1.1.1
Could definitely be worth a shot, especially if you’re planning on running other game servers down the line - that repo I linked to has a ton of game server configuration (“eggs”) on it. Hell it even has some eggs for non-game servers, like if you wanted a Mumble/TeamSpeak server.