NebLem

Almost all alternatives will be based on Open Street Map (OSM), and your mileage will very on the amount of detail from your local contributors. The two I primarily use are:

CoMaps (community fork of Organic Maps) has a clean intuitive interface and a decent router algorithm. Lots of developer energy and good community governance. Offline first, allows some OSM editing, quick to load and routing. Downsides are its limited feature set and configuration.

OsmAnd is a bit older but includes more routing options, near full OSM point of interests (POIs, locations like stores, buildings, etc) editing options, shows more POI types (configurable but can get noisy), has optional Mapillary (community Streetview style project unfortunately ran by Meta) integration, optional weather data, over and under layers from other sources, and optionally incorporates Wikipedia and Wikivoyage data filling in some gaps. Its interface is a bit more clunky, and somewhat slower, but it does a lot. Get the OSMAnd~ version from Fdroid, which has most of the “pro” (paid) version but without Google services. The actual paid version does have Google reviews and more POI search engine, but you’re using Google again.

Both are offline first but also both suffer from no review system integrations or traffic integrations (no Waze/GMaps reporting of slow downs or speed traps).

https://marginalia-search.com/ is pretty great for a different approach to search. While not exactly what you were asking for since its free, you can definitely pay via donations if you find it valuable.

And if you don’t want Signal because its “too centralized” for whatever reason, there’s DeltaChat, SimpleX, and good ol’ XMPP.