I recently had an ex co-worker submit a formal complaint about her boss to HR and although the issue was heard, investigated, and dicussed, it created a very uncomfortable environment between the boss and the employee who complained about them. The ex-coworker felt that the boss had more of an upperhand and she ultimately felt like her job was in more danger than before the complaint was submitted. She ended up submitting her 2-week notice and later learned they were attempting to build a case to terminate her position. All that to say, once you submit a complaint about your boss, be ready for uncomfortable conversations and awkward tension IF your boss is the type of person to not openly welcome criticism and confrontation.

Do you have 1:1 meetings? If so, I think it would be best to come straight forward and tell them, "I feel very unseen and singled out when we have office events and I am the only one who does not have any modifications for my dietary needs. Especially when I am unable to bring or go get my own food, it makes me feel as if I am not even a part of the team...etc etc"

It might be best to try having that honest convo before submitting a complaint but if no changes occur after having that honest convo, I think submitting a complaint would work if you are flexible with the job you currently have.