Dear Hans,
Thank you for your reply.
Here is the missing MWE. (I will also try to attach it.)
% mwe
% document is an English translation of Arabic text; all annotations are in English.
%
% concerning footnotes to Arabic text:
% numbers in body should use Mashriki numbers (e.g. ٠١٢٣٤٥٦٧٨٩), and appear between parenthesis
% numbers in footer should use Arabic numbers (e.g. 0123456789), and without parenthesis
%
% MWE uses dejavu for English and Amiri for and Arabic. Amiri is availble at https://www.amirifont.org/
\mainlanguage[en-gb]
\setupdirections[bidi=global,method=one]
\starttypescriptcollection [amiri]
\starttypescript [serif] [amiri]
\definefontsynonym [Serif] [file:Amiri-Regular.ttf] [features=arabic]
\stoptypescript
\starttypescript [amiri]
\definetypeface [amiri] [rm] [serif] [amiri] [default] [fallbacks=latin-fallback]
\stoptypescript
\stoptypescriptcollection
\define\setarabic{
\setupalign[r2l] \righttoleft \switchtobodyfont[amiri]
}
\define\setlatin{
\setupalign[l2r] \lefttoright \switchtobodyfont[dejavu]
}
\setupnotes[footnote][]
\setupnotes[arfootnote][]
\definenote[arfootnote][footnote]
\setupnotation
[arfootnote]
[before=\setlatin,
alternative=text,
]
\setupnote
[arfootnote]
[headstyle={\switchtobodyfont[amiri]},
textcommand=\footnotenotenumbercommand,
alternative=text,
]
\protected\def\footnotenotenumbercommand#1{{\high{({\convertnumber{arabicdecimals}{#1}})}}} % unexpected results
% \protected\def\footnotenotenumbercommand#1{{\high{({\convertnumber{abjadnumerals}{#1}})}}}
% \protected\def\footnotenotenumbercommand#1{{\high{({\convertnumber{default}{#1}})}}}
%
% `\detokenize' variations, for comparison...
%
% \protected\def\footnotenotenumbercommand#1{{\high{(\detokenize{\convertnumber{arabicdecimals}{#1}})}}}
% \protected\def\footnotenotenumbercommand#1{{\high{(\detokenize{\convertnumber{abjadnumerals}{#1}})}}}
% \protected\def\footnotenotenumbercommand#1{{\high{(\detokenize{\convertnumber{default}{#1}})}}}
\setupbodyfont[dejavu,11pt]
\starttext
\setarabic
مرحبًا\arfootnote{Annotation text.} % expected footnote `(١)`, got `1arabic`
مرحبًا\arfootnote{Annotation text.} % expected footnote `(٢)`, got `2arabic`
\stoptext
%%% end of mwe