There are no duty cycle limitations for 900MHz in the US. Its regulated largely like 2.4GHz (see 47 CFR § 15.247). There are rules for frequency hopping systems that limit the amount of time you can dwell on any given channel, but there are less restrictions on non-hopping systems. High-ish bandwidth 900MHz radios are pretty common and can do multiple megabits per second (at least with enough signal-to-noise ratio, which isnt always practical over non-trivial distances).
The duty cycle limits by ETSI are in place because of the population/usage density. If FCC does not put in place a regulation there will no shared high bandwidth usage over a long distance in high density areas. Think of 2.4 GHz WiFi.
Can you share some examples of high bandwidth 900 radios? In my experience, it’s difficult to get bitrates above ~100kbps on 900 over any meaningful distance.
I work with industrial grade 900MHz radios, and most can do over 1Mbps... with enough SNR, which as I mentioned can be difficult. I would say a typical ~city sized network I've worked on tend to operate in 100-1000kbps modes, with real world throughputs maxing out at more like 300-400 kbps on typically 1-10 mile links.
Manufacturers include FreeWave, GE MDS, XetaWave, 4RF, and others. These are typically ~$1000 radios, so not great for hobbyist use.
In addition to Ubiquiti (already mentioned), Motorola (Cambium) also made some PTP and PTMP radios ("Canopy"?) that were quite popular in the WISP community years ago.
I'd be surprised if you can't easily find both on eBay.
