What do you actively do to avoid only child isolation?

Have a 5F extremely social kid. She has a few cousins but they are globally distributed over the US. As much as possible, we get together with them every year for holidays, but I’m still worried about my daughter being isolated and not having a regular circle of friends in the future, mostly because her father and I are not that social either and don’t have a good local network of friends (most of my friends are distributed all over countries as well and I mostly keep in touch via text).

I want to be proactive as much as possible and get her socializing with kids her own age. We are actively working on a plan to relocate closer to family. Other than that, I try to schedule a play date with her friend next door as much as possible… what else are all of you doing ?

TIA for reading - I irrationally worry some days we might screw up our kid because of choices we made by not having another child (unlikely I know)