I kept Rasboras and Bettas together for years. They never nipped. Some tetras of various sorts did, and livebearers, yikes. betta fins look like decaying plants to them, and once they taste, they go back. Nippy tetras nipped.
But in the right set up, Betta splendens that are able to swim (not the completely incapacitated expensive ones) are fine community fish. You just have to research the community carefully. No fin nippers. Midwater shoalers were fine, and even rummy nose and glowlight (NOT Glo-tetras - I mean the natural one) tetras made solid tankmates, for years.
Until about 20 years ago, Bettas in shops around here were usually found swimming in sales tanks with other species - one male with a huge number of tetras or rasbora, Corys, etc. The selling in cups only really took off when Bettas became super popular and space became an issue.
Bettas tend to be too slow to catch tankmates, and lose interest fast unless the tank is too small for the fish in it.
I bred wild caught Betta splendens from Laos, and close to wild form pla-kat from Thailand. In both cases, in larger tanks, as I raised the fry into adulthood, I had large Betta communities with multiple males. The psycho fighting may be because they were bred for gamblers, and selected for maximum aggression.
The first generation from the wild males all had territories and did a lot of showing off to scare each other, but as long as I didn't move things around to mess with their turfs, they got along pretty well - better than the males of the Apistogramma dwarf cichlids I was growing out.
I'm not trying to be a contrarian, but these are things I did for 40 years when I used to have community tanks. Over that time, since I have almost always had several tanks, I must have kept 30 Bettas with never an issue with non livebearer (mollies like fins...) tankmates. I never kept them with the nippers, like silver tips, ternetzi (the one used to make glo tetras), zebras danios, or many of the barbs. I did my homework first, since I find reading about fish to be fun.