Hi,
You can update the command for ConTeXt as follows:
Graphically:
M-x customize-variable *↵*
TeX-command-list *↵*
find the appropriate section for ConTeXt commands and change it with (e.g.) "context --purgeall %t" (see attached image).
Apply and save.
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Using the init.el you can also create your own commands:
(custom-set-variables '(ConTeXt-Mark-version "lmtx") '(ConTeXt-engine "lmtx"))
(eval-after-load "context" '(setq TeX-command-list (append '( ("context" "context --purgeall %t" TeX-run-command t :help "Run context (lmtx)") ("luametatex" "context --purgeall %t" TeX-run-command t :help "Run context (lmtx)") ) TeX-command-list ) ) )
I hope this helps.
Lizardo R.