I use an iPhone 11 mounted in a SlipGrip holder. It has never budged in any riding condition. The newer iPhones (and Galaxy phones) are waterproof.
I used to use Navigon app which was very good, but recently went out of business.
Scenic app is what I use now. It is made specifically for motorcycles. The maps are downloaded directly to the phone so cell reception is of no issue.
It can generate “extra curvy” routes from point A to B or start and end in the same place. You can create any route you want and share them with anyone. There are thousands of available routes that people have saved and rated based on various criteria. Its a very powerful and useful tool. The maps are always up to date and high resolution.
If you have a smartphone, there is simply no need for an “old school” Garmin. The hardest part is finding gloves that work on the touchscreen.