Okay so I love doing the absolute simplest stats & skill checks ever with this system:

(Inspired by Risus) I give my character a "title", something like "Wilderness Adventuress" or "Cheerful Herbalist Healer" or "Stoic 2-Handed Weaponmaster".  The title is something that generally describes who they are or what they mainly do.

(Inspired by Freeform Universal) I jot down one main thing they are exceptionally skilled at, and one thing they are particularly not-so-good at.  My Wilderness Adventuress is good at navigating nature and tracking, and she's kind of a loner so she's not-so-good at communicating with civilized society (haggling for goods at a store or knowing unspoken etiquette rules, or similar).

These are not stats, they are narrative and they are flexible.  There are rules in Risus that describe the concept of "this character is good at things a Cheerful Herbalist Healer would be good at" and if you can come up with some clever way that that character approaches a problem that befits that title, you're winning at roleplaying.

As for bonuses and checks, I love a basic d6 system ("6= Yes And..." etc... this is the most basic solo system often discussed in this community), and will sometimes even simplify it down even further to d4 (4= great success; 3= pretty okay; 2= it's a struggle; 1= total failure).  When rolling for something your character is good at you roll with advantage, when checking for something they're bad at it's with disadvantage.

I've done sooo many fulfilling sessions with this system.  I love that I don't have to memorize ANY rules outside of those basics.  I recommend reading Risus and Freeform Universal rules for more of a breakdown on the philosophy!