I can recommend wasabi.com, they are a lot less expensive but also offer a full S3 api.
Side note: I’ve heard about Wasabi for a long time; they actively advertise on APMs Marketplace audio program about how much cheaper they are then S3 for storage and transfer. Backblaze B2 would’ve also been an acceptable alternative to S3.
Usually from free or niche products of well known big companies. S3 will probably not be deprecated over night without a appropriate notice period as half the internet depends on it in some way as you can see on S3 outages.