I use AllTrails.
There is a free version, an annual subscription version (~$29?), and a lifetime version (~$99).
Only the paid versions allow you to save your data when off-grid or after a phone reset. All have some off-grid support, but I wouldn't trust the free version for that. In fact, I use AllTrails as a go-to suggestion, relying on traditional techniques instead (paper maps and paper trail guides, perhaps a compass).
I'd recommend downloading the free version to see if you like the UI and trying it on a local day hike. They have a huge collection of hikes worldwide. I have the lifetime license.
AllTrails also allows you to record and share your hikes with their online community, and I think to add new trail hikes.
For thru-hikes, like the Pacific Crest Trail or Appalachian Trail, hikers typically use Guthook/FarOut. I'm a beginner with that, but looks to be totally worth it. I was impressed with their updates of water source conditions (even with videos taken by trail angels and other hikers), weather conditions, warnings, and locations to camp on the map along each trail section. This info is available even off-grid.
Guthook is subscription, but totally worth it for thru-hikes. Not sure if it allows you to import tracks.