Notes:

• Do not forget to escape the $ by an additional $.
• Escaping ? like \? does not work. But you could use [?] instead

End result should be like this:

- "traefik.http.middlewares.r6tt-dev-web.stripprefixregex.regex=^/[a-z0-9/]+[^.][a-z0-9]+([?]+.*)?$$"