"sysupgrade -v /tmp/(name of bin).bin" (without quotes)
thing is, the graphical Openwrt firmware is in multiple bins, which are named
I have tried flashing the "sysupgrade" one, but the router terminates all SSH connection until I restart it.
(For the record, my router is EA7500 V2, not V1)
I apologize if formatting is awkward, I tried to space everything out so that it is clear and not confusing.
Just to add to what @frollic said, there shouldn't be a need to manually restart to regain ssh connection, terminating the connection after sysupgrade is normal, try waiting 3-5 minutes after sys upgrade and then try ssh again, it should connect without manual restart.