I have just published a set of full-battle rules for the High Middle Ages (Baron's War, Crusades, Scottish War of Independence, etc.) – my club games a lot with app-driven rules which replace the rule books and charts with simple web apps to determine modifiers. This keeps the table free of clutter, and makes games play faster. We have been publishing these apps for a couple of years now, so that other people can enjoy them. They are very easy to learn and use – we play a lot of ADLG, but for conventions, especially, you need something simpler.
The new system is called "Chanson de Geste" and can be found at:
link
We did a set for the late Middle Ages a couple of years ago, named "Bloody Dismal Fight", which you can find on the same site. (It was designed for use in remote games over Zoom, during the pandemic, so the app rolls all the dice for you, which not everybody likes…)
link
Give them a try – I am always happy to hear comments and to try and improve the games. (Right now I am painting Welsh for LLewellyn's 1282 conflict!)