[NTG-context] problem with MkIV/TeXlive/TEXMFCACHE

Dear experts, I want to use ConTeXt MkIV as supplied by TeXlive 2021. After installation, I ran "mtxrun --generate". I also tried "context --generate". Both create output in the wrong place. The TeXlive documentation says that ConTeXt uses TEXMFCACHE, which uses the default $TEXMFSYSVAR;$TEXMFVAR in my texmf.cnf. My TEXMFSYSVAR is /var/opt/texlive, but ConTeXt doesn't use it. Instead, it creates /opt/texmf-var and creates its output there. I don't understand why it used that path; I've never used or configured it. How can I convice ConTeXt to use TEXMFSYSVAR? Or is this a question for the TeXlive folks? Thanks for looking at this. Regards, Rainer