Up until last year at least swappable batteries were still common in lower-end smartphones. Generally none of those OEMs sold spare batteries though; even when many high-end models had swappable batteries, up until 2015/2016-ish, almost no OEMs sold spare batteries. I think it was the beginning of 2016 that LG actually started selling spare batteries, the same year they produced their last two high-end smartphones with swappable batteries.

Even though swappable batteries do continue on the low-end, I think maybe [in the US] only Motorola actually makes spare batteries available for consumers to purchase, even for devices that don't have readily swappable batteries. I think this year Motorola will ditch swappable batteries, pretty sure, but will supposedly continue to make spares available for select models via Ifixit.