I'm in a similar boat and getting customers to whitelist IPs is always a big ask. In the best case they call their "tech guy", in the worst case it's a department far away and it has to go through 3 layers of reviews for someone to adapt some Cloudflare / Akamai rules.

And then you better make sure your IP is stable and a cloud provider isn't changing any IP assignments in the future, where you'll then have to contact all your clients again with that ask.

They're mostly non-technical/marketing people, but yes that would be a solution. I try to solve the issue "behind the scenes" so for them it "just works", but that means building all of these extra measures.