Unfortunately there is very little content of the M Routes online, those are used to represent the various Expressways. But recently UNRA and KCCA have installed signs marking the M routes (https://archive.ph/gahHR & https://archive.ph/fmOPk <- Images from 2025 showing signs showing the M3/Entebbe Expressway).
At the moment the entire M3 has already been marked by UNRA (See image: https://x.com/kiyagaedwin/status/1691133674807349265) and several road sign design representatives such as Kiyaga Edwin Raymond (Senior Highway Design Engineer at MowT) on Twitter have indicated that they are designing and preparing for the installation of road signs on the interchanges in Kampala including several intersections of the Northern Bypass (M20) and Southern Bypass (M21). (See proposed Kisaasi Interchange signage design (https://x.com/kiyagaedwin/status/1756218002431758754/photo/1) showing M20 and M21 marked). I am talking to them if they can give us an official document containing information about the M Routes.
-- DigitalSeb01