Free backlinks

A few years ago I found a pdf guide on generating 100 free high DA backlinks by creating profiles in different websites.

I have around like 5-6 guides here in BHW but I wonder if there is anywhere a guide that summarize all of these opportunities.

If not, please share any method you know of

Already many method shared here. You can find some working tips in pinned threads in respective section.

Check the posts of @Rachmaninoff and you'll find a treasure trove.