I went through this with ds3 - over the years I signed him up for several things, and offered others, but nothing stuck - in the end, I stopped because it seemed a waste of time signing him up for things that he then quit.
In his mid teens, a friend suggested he go along to the hockey club his friend was in (that his dad coached), and he did - and not only did he love it, but he is good at it. He and his friend moved up to a very good hockey club in Glasgow, and he'll be joining a clunpb when he goes to university.
I guess what I am saying is that, whilst being in a club is good, it isn't for every child, and sometimes it's better to let them find their passion.
Maybe take him along to some different things - you've suggested some things, and he's shown no interest in them, but maybe the next thing you suggest will be the thing he'd like to try - but if he doesn't want to stick with them, it's not the end of the world.
Have,you considered Beavers/Cubs? All my dses did these at some point, and ds1 and ds2 did enjoy them.
Is there anything in particular that's making him nervous about joining a club? In dd1's case, she didn't want to do anything because she thought there'd be some sort of competition involved and she hates that.
Do you want him to learn a skill, or improve on a skill (e.g. swimming club), or do you want him to do a more social activity? I've tried to get dd1 to swimming club but she hates the idea (she's a good swimmer) but she's started going to orchestra with a friend, and that's a social activity as well as improving on a skill.
Do any of his friends do anything he might like to do too?