'Adventure bike' is currently nothing more than a buzz word. You can have an adventure on any bike as long as you enjoy riding it and an adventure doesn't have to be very far away and the bike doesn't have to be very exotic.
I have a Croix de Fer. I've toured through the Alps with it fully loaded and currently it is fitted with CX tyres for fun in the local woods and bridleways so for a jack of all trades adventure bikes, gravel bikes call them what you want will do most things asked of them and provide quite a lot of fun too.
On the road it's a little dead and not very quick, but a lot of that is down to my legs and lungs rather than the bike, I'd have no concerns doing a longish Audax on it but I have a road bike for such things.
With the latest trend for carbon gravel bikes the best of both worlds is probably something like the Genesis Datum, other brands are available, I just have a thing for Genesis! It is lighter and faster than the CDF, it doesn't have rack mounts but the modern trend is bikepacking luggage anyway. Such bikes would comfortably keep up with a chain gang on slick tyres (if my legs and lungs were up to it) and go anywhere you pointed it on knobblies. If I were starting again I'd go down that route and have just the one bike - in fact I bought my wife a Datum for her birthday last year and we ride the same size frame.....