UTF-8 and the Tufte Book document class

[R H van der Gaag]

Hi all,
I am writing a book using the Tufte Book document class, with the Tufte font included through ``\usepackage{ETbb}`` in the preamble. This works fine. But the encoding is T1, and producing a PDF fails when I change it to UTF8. I intend to add some Chinese text, and I either have to get UTF8 to work with this document or get Chinese characters with the present T1 encoding (but that is not the preferred approach, given that LyX 2.4 will be UTF8 throughout, if I am not mistaken, so I might as well get that sorted now). The main language of the document is Dutch, with bits in German, ancient Greek, French, and other languages. I am using LyX 2.3.7 on an M2 MacBook Air and an M1 iMac.

Any helpful hints are much appreciated.

RH