Firstly, no point trying to get Internet to a non Smart TV. And if a TV lacks LAN or Wifi, its not Smart, so can't make use of it.
A non Smart TV can be converted to Smart-ish using a plug in box, the exact one to be what fits your needs, such as Amazon Firestick, Roku, or any of the no name Android boxes out there.
Powerline adapters do mostly work, but are frequently a bit naff, either in performance or the constant need to reset them because they sudden just seem to stop working. I use them to get wired Internet in my garage, currently its a TP Link one at provides 2 ethernet and wifi on the remote plug. In larger houses, they can be problematic, but generally fine in normal homes. Sometimes you find a combination of sockets that works better than others, so sometimes a bit of experimentation is needed.
Wifi extenders are universally crap. Always.