I like Charis SIL for body text. In my ~/.fonts directory, I have the four CharisSIL-B.ttf, CharisSIL-BI.ttf, CharisSIL-I.ttf and CharisSIL-R.ttf files.
In LyX, i've gone to document settings, selected "Use non-TeX fonts." Charis SIL does appear in the font menu, so clearly the font exists and is being recognized as such.
Then when I view the document, I get:
etc. etc.(/usr/share/texlive/texmf-dist/tex/latex/base/fontenc.sty
Package: fontenc 2021/04/29 v2.0v Standard LaTeX package
! Font \TU/lmr/m/n/10=[lmroman10-regular]:+tlig; at 10pt not loadable: metric da
ta not found or bad.
! Font \TU/lmr/bx/n/10=[lmroman10-bold]:+tlig; at 10pt not loadable: metric data
not found or bad.
<to be read again>
! Package fontspec Error: The font "CharisSIL" cannot be found.
! Font \TU/CharisSIL(0)/m/n/10=CharisSIL:mode=node;language=dflt;+tlig; at 10pt
not loadable: metric data not found or bad.
<to be read again>
Now the funny thing is, in my org-mode export setup I have:
#+LATEX_HEADER: \usepackage{fontspec}
#+LATEX_HEADER: \setmainfont[Ligatures={Common,TeX}]{CharisSIL}
#+LATEX_HEADER: \setmonofont{Inconsolata}
... and it works. So xelatex on my system has no problem with this font -- but LyX does.
At this point, I've spent the majority of a working day first fighting with an intractable problem with org-mode export, and now fighting with basic rendering in LyX. I would like to stay focused on solutions here, but it has been a frustrating day of not writing but rather beating my head against fruitless web searches.
(After resolving those, I will have a different problem to report, where side by side subframes are being rendered vertically rather than horizontally aligned as they are in the editor.)
hjh