I've been in that situation before too, especially when signing up for services where I didn't feel comfortable using my main number. What worked for me was using a
non VOIP number. I came across Tardigrada.io when I was searching for something secure and private. It was super easy to get a temporary number, and it didn't require me to jump through any crazy hoops. I used it for a while without any issues, and it kept my personal details safe.