I found this route is pretty chill, the river trail starts at the Deschutes River State Park (just east of the city of The Dalles Oregon.) A flat gravel / rock trail on the East side of the river that used to be a rail line back in 1910, but a competing rail line on the west bank rendered it unnecessary and thus we have an brilliant trail.
Route here: https://ridewithgps.com/routes/27209444
The first part of the trail is flanked by smaller hiking loops (posted no bicycles). But the main ridable path goes out for 20miles one way. The path provides a fun day on the bike with amazing views each side of the river. Changing terrain of smooth hillsides, rocky crags with eagle caves and rocky washouts from where other rivers meet the main Deschutes. The trail is not a smoothtop road, for the most part the trail is flat and somewhat packed dirt with occasional small rocks or light gravel, there are sections of larger shale type rock, but those sections are not long and easily navigable if on a mountain bike.
Many rivers join the Deschutes river , large valleys from the East so back in the day there used to be large trestle bridges, but these have since gone, leaving steep, loose rocky sections that are impassable for the normal riders. Thus milepoint 20 is the furthest you can go, we tried to push on, scrambling up and down some sketchy sections with our bikes, we gave up after a few valleys. Maybe for a next time to make it connect over to the Mac campground to the South.
Required: Take a patch kit and tubes because this area can be riddled with sharp thorny goatheads – from a plant that grows in arid conditions and leaves nasty bicycle puncturing thorns,
Bicycle: Best ridden on a hardtail mountain bike or a full squishy mtb if you wish but bit of an overkill. I rode it on a cyclocross bike and it was fine for me most part.
Overheard: very hot in summer and rocky sections can be prone to snakes, so read the trail signs before entering.
At the end of the trail…