tl;dr: ibuprofen may be a cause as well.

I suffered from incredibly painful month+ long lasting chronic canker sores (technically apthous ulcers) for the first 3 decades of my life.

Doctors and dentists suggested all the usual triggers (avoid SLS, supplement with B vitamins, etc)

Then one day someone mentioned the connection of NSAIDs and ulcers, and I instantly realized mouth ulcers are.. ulcers...

I used to use ibuprofen occasionally, often enough to not correlate it to canker sores. Of course then I’d use more ibuprofen for that pain, get more canker sores, and be miserable for months.

Haven’t bought ibuprofen for 10 years now and they just stopped. I have used ibuprofen on a couple occasions since I learned this and both times I developed a canker sore. IANAD, YMMV, I’m just happy they’re gone