I bought a buzz TV, the classic box last year when I was living where power supply was 110 V. I am now living in SEA where there is double the voltage. Do I have to plug it into a transformer or these modern devices work work across the range. Thank you for your help in advance.

Typically they are 110/220 and all you need is a plug converter with is super cheap.  But they are always printed on the units in pretty fine print so you can easily check.  It probably says input 110-240V.

The Classic however conveniently uses USB-C as power.  So worst case it is simple enough to just get a basic  USB-C power supply locally and use that to avoid using any adapters.