The typical way to control a TV, especially a non-Roku TV, is via IR. Roku remotes control TVs through IR and Rokus through either IR or Wi-Fi. The vast majority of recent-model phones do not have an IR emitter which gives them no direct way to communicate with a typical non-Roku TV.
There is a possible workaround of sending a command to the Roku and having the Roku send a volume command via HDMI-CEC, but HDMI-CEC isn't always available, enabled, or reliably implemented. My TV implements HDMI-CEC fairly well, but I got annoyed by it being turned on and/or switched inputs when I didn't want it to, and since there were no detailed options to make CEC work like I wanted, I turned it off.
Banned but back. Because why not?
