> Thats just a matter of buying a decent IP

Please expand on this. Public cloud IPs would be on spam lists, and providers like Hetzner and OVH aren’t any better. Where does one go to buy a decent IP?

Use an IP reputation tool like https://mxtoolbox.com/blacklists.aspx

What you will find is that many dedicated IP's from larger vendors are fine.

I personally use Hetzner and don't have any issues with reputation at all.

I had troubles with Apple blocking a bunch of range IPs from OVH, because they don’t handle abuse claims. It didn’t show up in blocklists at the time, but was in practice unusable.

IME anything that can be purchased by an average developer is in some list nowadays and deliverability is always crap (with luck it lands on spam folder).