If I experience a mid-year qualifying life event (QLE) that allows me to enroll in an HDHP with HSA, can I switch my GPHC FSA to an LPHC FSA?

No. Enrolling in an HDHP with HSA would not allow you to change or cancel your GPHC FSA election to establish HSA eligibility or to enroll in an LPHC FSA. Per Internal Revenue Service Notice 2005-86, an individual who is covered by a GPHC FSA is ineligible for HSA contributions for the individual's entire period of coverage under the GPHC FSA , even after the individual has completely exhausted the GPHC FSA balance. Coverage in a GPHC FSA will render the participant ineligible to make or receive contributions to the HSA for the entire plan year.