I'd recommend buying a pickaxe using forageables (glimmermoss) or whatever the seller wants , with a q100-115 pick you will be able to mine the first level and maybe l2 with 10str...
Otherwise the strength needed depends on the q of the pickaxe/axe you can use and what you expect from mining...
As I started, mining was a hard task with ~10% per tick (first level, before mining update, shitty stats, no pickaxe, etc...).
Now I can mine most of the l5 with 100% pet tick which means 10 times faster, 10 times less energy needed.
As hermit you should try to hunt or try some baked goods, meat pie for example ?
So my conclusion will be, you can mine with any str, any tool it just depends on your expectations
