Hi,

Following the instruction from : https://wiki.contextgarden.net/Use_the_fonts_you_want

mtxrun --script font --list --file -pattern=*casual*


gives :

familyname     weight   style    width    variant   fontname       filename                                subfont   fontweight

lucidacasual   normal   normal   normal   normal    lucidacasual   /home/xxxx/.fonts/LucidaCasual.ttf



Then the following code should work :

\starttypescript [myserif]
  \definefontsynonym[LucidaCasual-Regular]    [file:LucidaCasual.ttf]
\stoptypescript
\starttypescript [myserif]
  \setups[font:fallback:serif]
  \definefontsynonym[Serif] [LucidaCasual-Regular] [features=default]
\stoptypescript
\starttypescript [myserif]
  \definetypeface [myserif] [rm] [serif] [myserif]    [default]
\stoptypescript
\setupbodyfont[12pt]
\starttext
The quick brown fox jumps over the lazy dog
\setupbodyfont[myserif]
The quick brown fox jumps over the lazy dog
\stoptext