Flipper zero doesn't really have a competitor, aside from maybe a bunch of bulky equipment that fits on a table. Such a feature phone would be competing against iPhones/Pixels, both of which are pretty secure and have dedicated security teams. Any new product would have to compete on price/feature/reputation, which would be tough.

The success of the Raspberry Pi proves that existence of competitors is no impediment to success with the proper connections with vendors and with the community.

The OpenWRT One is another example of collaborating with community trusted vendors to build a niche community based hardware product.

https://openwrt.org/toh/openwrt/one