I don't understand this. Why not trying the "shady battery" for cheap before buying a whole new phone? Even if you somehow don't trust their batteries, I see s10e batteries on ebay for ~10€. Just buy one of those and have them install it?

Every device I've ever wanted to keep after its battery started degrading (mostly laptops, but has happened with a phone too) I've either ordered one from ebay and replaced myself or went to a cheap local shop.

OE batteries aren't magical.