Sometimes I need to run ReplaceText on namespaces with content models other than wikitext. That used to work for me if I remember well, but the last time I ran it (a plain-text model in this case), it exited with an error message along the lines of "Wiki page ... does not hold regular wikitext".
Topic on Extension talk:Replace Text/Archive 2019 to 2024
At some point I was able to run replacements on pages with a plain-text content model. But guess what happened: for many of them, the content model was changed to wikitext. How can I 'mass restore' their models?
The original post was probably addressedd by this commit: https://github.com/wikimedia/mediawiki-extensions-ReplaceText/commit/a2b09220fee3864a6512c2e661dc6576636e1972 - I'll have a look later on to see if the other issue persists.