No, Optus uses bands that the Sony Xperia 5 ii should support.
From this website.
Optus is Australia's second largest mobile network operator, providing high speed connectivity over its 3G, 4G, and 5G networks. Optus is currently making a significant push into regional and rural areas with its $1 billion regional Australian network investment program announced in 2018.
r-spectrum.com.au
Optus uses;
Optus 5G
5G caught a lot of people in the technology industry by surprise. Expectation was that we wouldn't see 5G implemented until 2020 at the very earliest. But the tech industry moves faster than any other and 5G is already here. The key Optus band for 5G is n78 (3500 MHz) which it has deployed with 64T64R Massive MIMO antennas. Optus' 60 MHz channel means it can pipe around an extra gigabit on top of its existing 4G LTE network.
3.5 GHz does have a limited range, but beamforming technology has been demonstrated to provide similar range to that of 2.6 GHz. With 5G there aren't a lot of options as far as traditional external antenna systems go, 5G is such an advanced technology that we can't use old fashioned coaxial cables and patch leads. All 5G units worth their weight are all-integrated ODU style.
In the next year or two we'll see the introduction of mmWave 5G on Optus, who are looking at n257 (26 GHz) as their main millimetre-wave band. This is where things will get very interesting, and incredibly fast with trials showing data rates as high as 70 Gbps. Picking a 5G integration partner who understands the technology is going to become more and more important as the industry progresses.
Optus moved very fast on 5G. Our expectation is that Optus 5G will continue over n78 (3500 MHz) for the time, but an eventual refarming of its extensive 2300 MHz holdings is a near-certainty. Optus secured 98 MHz of 2300 MHz spectrum when it acquired Vivid Wireless in 2012 and portions of the spectrum are currently used for B40 LTE for the company's 4G Home Broadband service. It's R-Spectrum's prediction that an 80 MHz n40 5G carrier will be implemented in the coming years - possibly making the Optus 5G network the fastest in Australia.
Optus officially launched 5G services in November 2019 with an initial 290 sites, and expanded to 1200 as of March 2020.
TECHNICAL DATA
Evolution
NR (Rel. 15+)
StatusActive [Launched 2019-11-28]
Max. MIMO
Massive MIMO
Max. Modulation
256QAM
Carrier Aggregation-
NR BANDCHANNEL WIDTHSTATUS
n78 (3500 MHz)
60 MHzActive