AFAICT -- and I would be happy to see counter-evidence -- all the unlicensed spectrum suitable for LTE or 5G is in the 5-6 GHz frequencies. The physical characteristics of transmission don't change, so one might as well just deploy the cheaply available 5GHz wifi systems -- you don't get an advantage by using LTE or 5G protocols.

i suppose if you only had relatively low data rate applications you could use 900MHz, but there's a dearth of CPE. 900MHz unlicensed has slightly more bandwidth than a single 2.4GHz wifi channel.

Might as well use 8.0211ah there. It's not like you can get consumer equipment that supports the 900 MHz ISM band for LTE.

You can probably drop it down some more and use tvws spectrum. Probably will be alone there

TVWS channel allocations often don't align neatly with duplex paired 3GPP bands, meaning you might need multiple adjacent TVWS channels.

In addition, in many countries the TVWS regulations only cover specifically authorised devices which adhere to TVWS standards (which 3GPP doesn't), and create a whole host of challenges for the client devices (handsets), which don't understand TVWS rules, and need their transmit power to be controlled by the base station, which isn't necessarily aware of the client location, or authorised within TVWS rules to query the TVWS database on behalf of the client.

Rules are different in each country of course but most unlicensed frequencies can only be used with mechanisms that leave space for other users (networks) like listen before talk or restricted duty cycles. Cellular technology isn’t built with shared access to spectrum in mind although there is/was some effort to add it (LTE-U, 5G-NR-U).