Is even the most mild exercise a trigger for anyone else?

Definitely been there. Post-exertional malaise was a very limiting symptom for me for years. Like you described, even just gentle activity would leave me weak and exhausted for days.

With a lot of trial and error, I found that recumbent restorative yoga poses helped to ease joint and muscle issues and increase circulation. This was important for me because I was mostly bedbound, which definitely took its toll in deconditioning. Rebounding with a porch swing also helped with lymph and blood circulation when I wasn't able to do anything else. Any other activity - even a gentle walk, singing a song, or going up the stairs in my house - was something I'd "pay for" afterward.

Very cool to hear about your ozone IV results! It's understandable that you wanted to try a little more activity.

Another one that had severe post-exertional malaise (I just called it exhaustion! LOL) from even the most minor exertion. Stairs were a no-go for me, and I sing (believe me, no one wants to hear that!) - but just walking to the bathroom and I'd pay for it at one point.

I started with bed yoga, but it looks kind of the same as recumbent restorative yoga, although I only took a quick peek at it. I've been able to transition to a few more poses - until I started walking. LOL. Now I have to balance when I walk with how much and what kind of yoga I do, but my body needs the yoga daily, especially after being bed-bound, then house-bound for many months again.

I did just walk yesterday again, and combined with careful yoga to not inflame anything more than it was (read, lots of ice!), and I didn't sleep too bad last night, and hopefully better tonight. It's a process, for sure!

i have had PEM from the start of my illness - could be knocked back for a week if i overdid it

i still have it but its much improved and can do 45minute workouts now

i followed a lot of the recommendations from Dr Sarah Myhill in the uk - a GP now in private practice as a CFS specialist

she has some papers and books published on mitochondrial malfunction which is believed to be the cause of it - often driven by oxidative stress at the cellular level and damage to the mitochondrial membranes
therapies include all of the below in combination ( from memory so not a complete list)
-exogenous anti-oxidants - vit C, vit E, B vits, Co-Q10, polyphenols etc
-glutathione support - NAC, ALA,
-energy transport support - Acetyl carnitine, magnesium
-mitochondrial membrane repair - high quality lipids, phospholipids
-ketogenic diet - fat/ketones burn with less free radicals = less oxidative stress = helps break the cycle

in my case i believe inflammation from lyme and bart and maybe mycoplasma had broken the energy metabolism resulting in more oxidative stress in a self re-enforcing loop.
so the more energy you try to burn the more oxidative stress you create and the resulting PEM sets you back days / weeks

its a long road back and you have to avoid PEM and take only incrementally increase exercise very gradually - initially from a very low level

there is another post in the first page on exercising with Lyme - and all of these points also apply