Adventure tour company recommendations for 25yo please

[Willowskyblue]

Can anyone recommend adventure tour companies for a 25 year old please - perhaps to South America or south east Asia, or anywhere in between? Trip duration around 3 weeks to one month
I don't think DC would enjoy an 18-25 type tour with lots of partying but maybe something with a bit of adventure and culture. He's mad about art and animals!
It's for a present so I want a few ideas to float.

Budget ?

adventure? Mountaineering? Sports ? Off the beaten track?

on his own?

@itsthetea adventure, no mountaineering, no sport. Very happy with off the beaten track. Re budget, c£3-4k.

And he'd be going on his own.

Exodus and Explore do solo holidays, or pay premium for single occupancy. Sometimes there are offers but for that budget you are probably looking at Europe, N Africa or India.
In the past the holidays were more walking or cycling but these days, the holidays lean towards more comfortable.