So far I have almost 100000 miles under my belt, north of the Mexican border, and up to the Arctic Ocean.... as a solo traveller. I far prefer doing my own thing, and pleasing myself. Here are some of the ways I meet folk along the way. After all, travel is much more about the folk you meet, than (almost) anything else.
For that reason I like staying in hostels (they are no longer called youth hostels) where I have other travellers with whom to share experiences... while cooking and eating a meal and in the common areas. They will tell you where they have just been, what the road is like, what they saw, etc., and may even have you going out looking for things you had never heard of. (Most hostels have private rooms, often with en suite.)
Campgrounds are another great opportunity to meet other travellers. If you do not want to tent it, many have cabins, some of which are self contained and quite luxurious. Usually cost about the same as a hotel room, but a much greater opportunity to meet the 'next door neighbour'.
And then there is when you go into a place to sit down for a meal or a cuppa, don't go choose an empty table or stall, just peruse the place, and look for someone who is alone. By simply asking 'Would you mind if I joined you?', you will soon find out if you are welcome. And if you are not, well, you are no worse off. Not everyone wants company, but those who do, are often among the most interesting folk you will meet.
And finally at rest areas along the way. Rather than just rush in and out, check out the travel information. Others who do, will often share with you where they have been, what they have seen, etc.
There are so many ways to meet interesting folk on the road, but to meet them, you have to be one.
Lifey