How to get Netflix etc onto a TV via a smartphone?

Do you have a laptop? Use your phone to make a wifi hotspot using its mobile data, connect the laptop to the hotspot, then plug the laptop into an HDMI port on the TV.

Same also goes for a desktop PC/Mac, if you have one of those you can take along. A few phones will also do display output over their USB-C port, so with the right cable you can skip the PC and plug them right into HDMI.

Theo

There are a few ways to do this....

It depends a bit on the capabilities of the TV, and the phone.

Some TVs can be connected to a network and will be visible on the network as a device you can "cast" to. If the TV can do this, then I would go for a standalone wifi access point. It can be used to create a wifi network, that the phone can join, and also connect to the TV via ethernet.

The device needs to be in Access Point mode. Importantly it also needs to have its internal DHCP server enabled - so that it can hand out IP addresses to both the ethernet and wifi devices connected to it. Once the phone and network are on the network, use the cast icon in the netflix app on the phone.

If the TV can't act as a cast target by itself, then you may need two bits of kit - a "mifi" style mobile mobile network wifi router (with a sim card (real or virtual)), that can create a hotspot joined to a 4G/5G mobile network. You will also need something like an old chromecast or amazon fire tv stick that will plug into the TV's HDMI and give it a wifi capability plus software to make it look like a device you can stream to.

Then you would connect both the TV and the phone to the mifi network. (make sure the settings on the mifi are not isolating the wifi devices from each other - they need to be able to communicate locally - not just access the internet).

If you have a modern fairly high end phone that supports thunderbolt video over its USB C port, then you might even get away with a basic USB C to HDMI adaptor - plug the phone into the TV and use it as a big screen.