Hetzner VPS, proper reverse DNS, SPF, that's all, not even DKIM. The only big ISP that doesn't like my mails is AT&T and I couldn't care less (in Europe, rarely have to deal with people @att.net).
I was running my own mail server for nearly 10 years on Hetzner. Prior to that on other hosts and in the distant past at home. Running mail servers is something I have done professionally and successfully.
The last time I moved boxes as I had many times before. I was on clean IP range but I had no IP reputation at all. In the past this wasn’t such a problem, especially with SPF, DKIM, rDNS, DMARC, server-to-server SSL etc. Around the same time I started having to deal with organisations (legal, etc for a death in the family and later rent) rather my my own circle of friends. It became extremely apparent that my mails weren’t hitting the inbox. But they were being accepted. This was extremely problematic.
I was in the group stating that running your own mail server isn’t hard. I still say that. The hard problem is convincing the big players to let your low volume domains and IPs hit the inbox. I begrudgingly gave up my MX servers last year.
Of course, there are some mails where I don't know if they landed in spam or I just didn't get a reply.