If you want turn-by-turn, I don't think you will find an app that can guarantee the exact route you have planned. All navigation apps that I know of (including dedicated GPS devices) will recalculate the route using their own routing algorithm and the maps in the app.
How much the end result will deviate from your original route is hard to predict. I try to use devices or apps which allow me to load both tracks and routes. I visualise the track, which will always be exactly the route I planned, but does not support turn-by-turn and than load the route. That way I can see where the two are different. It also allows me to easily deviate from my originally planned route and pick up on it further on based on the track.

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Belgium to Nordkapp via Iran | Discover Overland | Destination World

If you are renting a bike for more than a few days, then buy a cheap charging cable off ebay/amazon (some come with multiple ports, you want at least 2.1amp to keep up with the drain of navigation apps). Take it along with some basic tools and cable ties, and fit it to the bike.

When we rented bikes from Pop bike in Chaing Mai, and M2R in Marrakesh, the owners of the rental companies were more than willing to help us fit our phone chargers and garmin montana cradle and charger.

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https://fernsforays.wordpress.com/

If your that worried about where u r going buy a roll of surgical tape, write the road number/turning /town name on a strip then stick on your tank in route order and pull off as u go.... Save the phone for when u get lost

I am something of a luddite, I have a car type satnav that fits into my tank bag, but I cannot see the display in bright sunlight, and i hate taking my eyes off the road, gave up with smartphones a while ago
I keep a couple of old fashioned Nokias for text and calls
on our last trip my nephew used some sort of maps in his phone but with roaming turned off, however he used cycle routes as it did not provide motorcycle and he wanted to avoid motorways
it led to some rather long hours in the saddle, as every time we started to get moving the damm thing would direct us up another narrow track or back road

I prefer to use a map, I put a card in my tankbag with the road names, the directions, and the various towns I need to pass through
oddly for many years now I have always got around with no problems, yes sometimes I am a bit out of touch but then I find the next town and pick up my direction again
nobody pinches maps from parked motorcycles, and you can write notes on them as well I have acquired a small notebook thingy for my travels, but only to organise accommodation etc using free wi fi, and to keep details of campsite hotels etc, although to be fair a small hardback A5 book has done me for years
I also keep a compass handy, perhaps I am a from another era !