Recently, when searching for free map software, I came across a tool provided under the link https://www.map.army/ and I think it's brilliant! What it does is access one of the regular free zoomable map services of your choice (e. g. OpenTopo) and let you apply the current set of military tactical symbols to it (APP-6C?). It's free to use and certain settings can be switched on/off or altered. Also, you can save your overlays, i. e. the symbols you put on the map.
As the maps scale, so do the symbols so that you can use the tool for any scale of combat, movement or level of conflict desired, from a firefight to Operation Reset. When you save your work, you can choose what symbols in a layer to save and export everything to PDF to. But be aware, maps in high resolution can easily accumulate to hundreds of pages. Of course, you can load copies stored locally from other computers, so working on a desktop PC and using a more mobile device on the gaming table is no problem.