I'm meeting a similar problem as many report here. Some itch downloads (not all) seem very hard to complete, and the main annoyance is there's no "resume download" option, one has to restart at every attempt and wait, wait... Looks like there's a problem with the itch server itself?
But now the free Lyndaria version download is insanely slow in this specific instance, that's new. Hope this info helps.
I'm located in Lebanon.