Yes, when I got covid the 1st time in Aug. 2021, I ended up with "the jelly legs" which lasted at least 12 months for me. I, too, have long haul covid and, after 15 mos., I still have some issues such as vertigo whenever I move my head or body too much, hand tremors, weakness/fatigue, and tingling all over my body.

I got covid a 2nd time in late July 2022 which re-weakened my legs so I got the "jelly legs" again. I was so weak at times (both times) that I used a cane, walker, and even a wheelchair.

My daughter got covid, too, and she described her legs as being so weak they felt "like jelly". That's the same way I had always described them.

Like your husband, I had an EMG study which showed nothing abnormal. I had three MRIs of which the 1st was interpreted to have shown a stroke (in an area that would not have explained my gait issues), but a 2nd neurologist claimed it was not a stroke but instead Wernicke's encephalopathy.

For me, the things that helped were: when my neuro found my low ferritin (indicating low stores of iron in my body) so I began to take iron every other day, rest/naps, plus sinus meds (as I finally saw an immunologist 13 mos after my 1st round of covid).

Tell your husband to hang in there, keep seeing doctors/ specialists until someone is able to pinpoint something. Get plenty of rest, drink lots of water, take vitamins (B6, B12, C, D3, fish oil/omega 3s, magnesium, and zinc). Those weak "jelly legs" are very real indeed.