Thanks will check it out. TLM at first flick-through looks very interesting. Your description of Infravision & Nightvision is great.
With TLM I really like the layout and choice of art. Bookmarks might need a bit of fixup?
For the Backgrounds, would recommend adjusting the layout so each one fits on a single page, rather than bleeding over.
There's a lot of depth in TLM, will have to take my time reading through it all.
For now, I'm planning to play your adventure with "The Littlest Brown Book" (here on itch as well), to give a 5e group a taste of '74 D&D, in both rules and vibes (and for me as DM as well).
If I ever got the chance to run an OSR sandbox, I'd look at TLM for sure. I wonder how it'd go with Gunderholfen?