No experience, but I had the impression Raw2dng would handle Nikon and most common camera RAW files, Raw Decoder similarly. Actually I rarely use the raw option in the phone's camera, as even after post processing, the various JPG options usually do a better job than I can. Yes, there are a number of apps that will process a DNG file that I have taken with my phone, but my issue is getting a raw file from a external camera into the phone in the first place. Processing in Lightroom is what I generally do as Snapseed on the phone is a bit of a pain. I use the ProShot app and often take a bracket of three shots. Snapseed will process the raw(dng) from my S7 so I imagine it will be so for yours. But I take a lot of bird pictures with my Nikon gear, and the phone's camera won't do for that. Raw2dng works fine the other way - if I take a raw photo on my phone I can use it to convert to DNG for processing in Snapeed or transferring to my laptop.

What i was hoping for is a way of getting the raw files onto my phone for subsequent processing.

Usually I transfer the raw files to my laptop using an SD card reader, then process them in Lightroom and sometimes Topaz AI Clear. (I've had Photo Mate for a couple of years and use it, and for difficult lighting it can make a big difference to use full information from a lossless file rather than the camera's compressed and stripped out JPEG.) Curious if using the camera JPEG is just 'good enough' for your purposes, or if you tried and disliked the Raw2DNG or similar apps.

Is snapseed free for samsung