Things my teens / early twenties and their friends do in a semi-rural area:
Sports & outdoor: running, ParkRun, indoor climbing and bouldering, water sports (sailing, paddle sports, power boats), cycling, martial arts, tennis badly,
Games: chess, mah jong, board games clubs, role playing games clubs
Volunteering: scout assistant leaders, local environmental groups, RNLI, lowland rescue (like mountain rescue), wildlife, food bank, community farm & rare breeds places
Young farmers & stuff they do
Lots of tractor and boat related stuff
Creative: brass band, am-dram, photography group,
Some are more under-25 focused and some have a wide mix of ages
It can take a while but it helps gives a few things a go he'll find friendly people who are pleased he's there.