Yes, those are the only cellular infrastructure companies besides Huawei. There was Alcatel-Lucent, but Nokia bought them a while back.
"They have assembled a small army of suppliers to build a virtualized network built on x86 hardware. ... Rakuten has no dedicated hardware except in its antennas, ensuring the upgrade to 5G will be straightforward. ... Chief Architecture Officer Tareq Amin said the network has "virtualized everything," including radio access, core, transport, IP, billing and operational support systems."
I'm not sure who this army of suppliers is though.