There are two primary alternatives to the IPO process if you want to go public.
The SPAC route. Special purpose acquisition companies (SPACs) essentially go through the IPO process on their own to raise capital and acquire the controlling stake in an organization. Instead of you going through an IPO, you become a public company by virtue of being acquired by the SPAC.
Direct listing. Also known as a direct public offering (DPO), a direct listing is a way to go public without working with an investment bank to underwrite the process and act as the issuer of stock. It’s faster and cheaper than an IPO. But you lose the protection and expertise of the underwriter, which puts your entry into the open market fully at the whim of market demand. Squarespace is one company that did a direct listing rather than an IPO.