Hi, I'm a new composer. If you're still looking for a musician, I would love to work on this project!
Here's a demo reel:
https://play.reelcrafter.com/6MwFR4GKT6m6J6iinj3BaQ (Specifically, White Hum is what would fit your project best.)
And a couple guitar songs on my Bandcamp that sound like a great fit:
https://timelessinterval.bandcamp.com/track/shaking-of-the-climbing-vines
https://timelessinterval.bandcamp.com/track/the-earth-turns-to-face-the-sun
https://timelessinterval.bandcamp.com/track/hourglass
As for a quote, I could do this for $40 per minute, or around $800-$1200 for 20-30 minutes of music. At that price, I can do the flourishes and extras for free.
I love making relaxing ambient music. Can easily incorporate all the instruments you mentioned in the post. Absolutely love Stardew Valley and A Short Hike! I'm very drawn to games that allow the player to relax and breathe, and give a sense of satisfaction in their work. That kind of game has been a huge comfort to me personally in my life. This sounds right up my alley, and I'm very interested in hearing more about the game!
Please DM here or on Discord (foogriffy), or email me at timelessinterval@gmail.com if you're still looking for a musician!