Sports might be the challenge. Many US states have athletic associations that handle most K-12 sports, and they require enrollment in an accredited member school. I am aware of several homeschool specific athletic associations in my area, but all are targeted towards religious homeschoolers. Not certain what secular alternatives would exist, but soccer is very popular & there are plenty of competitive academies that operate outside the school ecosystem.
Fencing for example, is usually clustered around external clubs. Very few high schools will have fencing teams, and in a lot of cities even the high schools that do have fencing teams will be kind of a joke compared to the club teams.
Of the others, there are either homeschool alternatives that are explicitly secular or at least not overtly religious, or there are competitive clubs. All the schools have track & field, but there is a large homeschool league. And the district has a few schools with pools and a few more with swim teams that practice at the city pools, but the local swim club is the one turning out the Olympians – but even then, it also seems to have plenty of offerings for kids who won't set a world butterfly record. Football, I imagine, is just so popular that the private/public schools take all the players.
Whether this is a positive or negative thing depends on the situation. Being precocious is something adults might think positively about (though not in all situations) but it's not something other kids usually admire.
For STEM-type stuff, see if there's a nearby Civil Air Patrol squadron. That alone has tons of extracurricular stuff: search and rescue, help with earning a pilot license, robotics, drill and ceremony.
Homeschooling is not for everybody, but if you go down that route there's a lot of support.
Yes, it's great if they provide these things, but it's a distant secondary concern. I'd rather my kid get a great education and miss out on these things, than get a poor education but have access to all these.
But of course, as others have pointed out, it's a false dichotomy. You can have both.