No ganglion block injections and am not doing anything proactive to get senses back. I do not think I have Hashimoto's. I've been on a constant low dose of l-thyroxine for about 40 years with no change in dose. No medical person has ever called it Hashimoto's.
The only way to prevent from getting Long-COVID is to keep from getting COVID.

I am Hashimoto’s/ hypothyroid c.20 years, with LC 4 1/2 plus years now. Lost my sense of smell with first infection gradually getting it back a bit after say 6 months only to then loose it for following years after second infection. My sense of taste as in sweet, sour, bitter, salty, umami etc is largely there but without the subtlety of flavours being correct. Texture is much more important, and some food loves like a good wood fired pizza now seems unpleasant. So I too burn things left on the stove as I can’t smell it! My smell problems seem rather minor in the hierarchy of LC symptoms ( completely fainting from postural hypotension)…just a few hours ago I had to lie on the floor of a shop without a chair/ bench as I had a dysautonomia ‘turn’, so I have followed DIY improvements. I recommend you look at the free membership ‘Abscent’ website with huge range of tips, discussions, personal reflections, on line courses etc. I have tried the Italian research of the supplement Glialia ( very finely ground um PEA-LUT) designed to pass the brain barrier, with a protocol of Alpha Lipoic Acid and smell training…look up the Prof. Arianna di Stadio talk etc. I did the first couple months, then just having the recommended break…I had some improvements from just the ‘one smell a day’ external smells, to some personal smells but not obviously food I am eating. But difficult to tell whether this is the Glialia regime or time/ coincidence! Though Hashi/ hypothyroidism does have a lot to answer for I have been made by my Gp to alter my thyroid hormone dosages as he was convinced I was ‘overtreated on levothyroxine’ ( I take T3 too) making my HR high, but yesterday got a specialist endocrinologist interested in cardiovascular - thyroid interactions, said ‘ no’…and on different doses did not notice any difference in my smell/ taste senses.