Something like this was brought up long ago https://forums.j-novel.club/topic/243/grimgar-of-fantasy-and-ash-printed-version/11 To summarize, those types of content are produced by the anime production committee and would require a whole separate license, and that license would have to be from a company that JNC has virtually no ties with, so more then likely it will not be happening.

I didn't know there was a Grimgar spinoff. I'd be up for this.

Glad to see that Grimgar is still doing pretty well over in Japan.