My partner has a new macbook pro and needs a monitor.  I have a Dell monitor which she used to use, but I am WFH at the moment so it is connected to my laptop.

We have an old Samsung television that has HDMI inputs, so we thought that might work.  She has a "dongle" HDMI adapter that plugs into her laptop's USB-C (??) port, and we connected an HDMI cable to this and into the television HDMI port.  She used this same dongle when using my Dell monitor so we know it works.

Unfortunately it isn't working with the TV.  All she gets is a very shaky image of her screen, it severely wobbles side to side and doesn't seem to have many colours.

Is it feasible to use an old TV as a laptop monitor?   If so, is there something we can do to make it work?  I wondered if its refresh rates or something that we need to coordinate, but I have no idea really (neither of us are techy).

All help appreciated.