In this situation, I’d probably go with a hybrid schedule — like 16:8 or 14:10 on days when you have a client lunch, and OMAD on other days (or 20:4, whatever schedule you prefer).
I used to be in consulting, so I totally understand the fact that sometimes the job requires you to have a meal with the client. That’s reality. Just fast as long as possible on those days, and do your regular IF schedule on other days.
I would try to eat as lightly/healthily as is socially acceptable with each client, and adjust how much I ate for dinner accordingly. But I’d continue to skip breakfast every day (unless I had to do breakfast with a client, which it sounds like is rare).
Sure, you might lose weight slower than someone who can do OMAD every day. But so what? IF needs to fit into your life if you’re going to be able to stick with it.
I do OMAD, so if I know that I’ll be going out to eat with a client, that will be my one meal for that day. My meal would be either steak with broccoli or chicken Caesar salad with bacon and an unsweetened iced tea…and maybe a bourbon if the occasion calls for it.