DIY kit recommendations

Partner is a huge pedal lover. Has bought and sold for years. Want to get a unique present and thought a DIY kit would be interesting just as an activity (don't think he'd actually use it). Anyone tried any and have a recommendation for something interesting? Bonus points if there's one he might actually use.

Can solder and is an audio tech, so not necessarily beginner level. An effect he may not have would be q bonus.

Thank you!