Which Ebook Companies Are Truly Reliable?

I’ve been researching different ebook companies to publish my work, but I’m confused about which ones are worth trusting. Are some better than others when it comes to royalties, distribution, or marketing support? How do you know which company is reliable for first-time authors? Has anyone had personal experience with any ebook companies that you’d recommend or warn against? I’d love to hear real feedback before deciding where to publish.