Sunny Boys support 208/240/277Vrms (some models and wattages don't support all of those voltages.)
The -40 and -41 have "Secure Power" batteryless backup, 120Vrms 2000W
Sunny Island (US model) is 120V. Use transformer or 2x inverters wired 2s for 120/240V. Use 4x wired 2p2s for more wattage. For grid-backup, single SI system crams all current through one phase, probably not what you want. SMA used to sell a transfer switch with autotransformer which had 2-pole pass through, transferred to single SI, avoiding that bottleneck. I installed multiple SI instead.
Yes, my SI are kinda outside, with extra waterproofing and rain shields.
SI and SB 5000US series have transformers and weigh 140 lbs.
Transformerless TriPower 30000TL-US is 30kW and 140 lbs.
Transformerless 7.7kW -40/-41 are 75 lbs.
When I hung my original 2.5 kW SWR-2500U inverters 17 years ago, I was probably stronger and they were only 75 lbs. I was able to carry them up a stepladder and hang them head high. Taking them down to upgrade was doable, but difficult When I hung 75 lb transformerless 10000TLUS under the deck...
diysolarforum.com
The new SB are hard to come by right now, probably a recent rush by consumers. Maybe supply chain too.
For my older grandfathered system, or offgrid or otherwise not needing Rule-21, old models are good.
I got lucky and bought a pallet of new in box inverters for about $0.10/kW. Couple more through Craigslist.
Even used may be good, but they have some finite life (SWR2500U my results were 34 years MTBF)