iMac 2017 compatible with the Mac mini ?

Short answer, No.

Long answer, the 2017 iMac cannot be used as a display for any other Mac as its hardware does not support it. If the MacMini is a 2020 or newer, it also does not have the hardware to support using any iMac as a display.

Be aware that several of the options in the 9to5 Mac article give sluggish display response. Luna goes as far as posting this advisory on its support site home page:

The red emphasis is theirs, not mine.

Those options are OK in an extra monitor for a Mini where you can park static items like pallets and open reference files, but would be totally unsuitable for a main monitor. The lagginess would be aggravating. Jerky videos; delayed keystroke response. Display options may be limited as well.

The standard external monitor remains the best choice for performance, options, ease of connection, and operational economy.

not as only display

there are third party apps that allow it

Use iMac as monitor: 5 Solutions - 9to5Mac

though the imac would be fully running so as such user alot! more powe than a normal real monitor