There's no use of requesting software update for this device as it reached end of life. There are other methods to get One UI 7 but I will not recommend those.
Currently there is no stable One UI 7 based custom ROM available but UN1CA ONE UI 7 ROM is in development and might take a few months for it to be ready. So I would recommend you to wait for the stable custom ROM otherwise you might face instability ...
Yes the update is already there as I'm using S21FE Exynos variant and getting VoNR in Jio. You just have to pop a Jio SIM and enable it for default data SIM and you'll get VoNR if available in your area.
