StreetZim

Pick any osm-*.zim from streetzim.web.app. The browser keeps its own copy of the file, so it needs as much free storage as the map is big; it normally stays until you remove it here. Safari clears a site's storage after seven days of use without a visit, and a Home Screen app has storage of its own — on an iPhone, add StreetZim to the Home Screen first, then pick the map inside the app. Streaming reads a map straight off archive.org through a small range proxy: nothing is stored, but tiles arrive slower than from a local file and it needs a connection. On a phone, streaming is usually the better first look.