If you are considering fibre options, the best wireless internet provider in Kenya is Telkom Home. The unlimited plan starts at Ksh. 4,000 with a fair usage policy. You may also want to consider limited options offered by Safaricom like 1 GB per day for Ksh. 100.
For fibre options, you may want to go with
Here is an article that discusses in detail about the available internet options in Nairobi: https://kenyayote.com/best-cheap-internet-providers-kenya-home-office-nairobi-wifi-wireless-services/