How Can I Make a Virtual Router on Ubuntu?

As many times mentioned, you can read how to share network connection here:

if it wont help, let us know.

just type

sudo apt-install hostapd

Then you can configure pass and name of SSID as you want at /etc/hostapd/hostapd.conf. but you must at least have a hotspot-able wifi-chip(wifi-card) on your motherboard. Vender like Broadcom(in my case bit old Machintosh) doesn't have the one, so not in use as hotspot but simply as accessing other wifis. you can google a list of which vender's wifi-card can be used as hotspot(^O^)Y just check your wifi vender ID by typing in my case

lspci -vnn -d 14e4: 

or

sudo lshw -C network

Secondly, fix Interface by typing sudo vi /etc/network/interface or if you are on newer version like Ubuntu 18.04, type

sudo vi /etc/netplan/01-network-manager-all.yaml

then

sudo systemctl enable systemd-network.service

next, need to stop /etc/network/interface(NetworkManager), by typing

sudo systemctl disable networking

check if interface is properly working, type

sudo systemctl is-enabled systemd-networkd.service

and (enable) should appear if all good. then, type

rfkill list all

if you get error saying ....soft blocked..., type

rfkill unblock wifi

then,type

sudo ip link set wlp2s0 up

then, check the interface name for wifi, by typing

ifconfig -a

the name allocated to your wifi interface is(mostly wlp2s0 not those like ens7 or enther9...) then finally type

sudo netplan apply

(oUo)Y----have fun !!!!