Ssense is Canada based but prices are inclusive of taxes and duties, they have a really interesting curation and know which up and commers to support from the get go as well as always having some interesting exclusives.
Need Supply & Co. US based and not so helpful with taxes and duties last time I checked (they may have improved since) but I do really like it for browsing for inspiration and discovering new brands which can usually be sourced elsewhere.
W concept is US based but it's a collection of small designer brands that ship from around the world. A lot of South Korean brands, also do the taxes and duties included thing and shipping always comes up cheap ($12 ish)
Moda Operandi is another great one, it's a US company but they have a European base in the UK so no issues with taxes, etc.
L'Exception is good of you're interested in French brands.
De Toujors is a really interesting French one that stocks a unique take on work wear.
I have a bunch of concept stores I frequently check in just from visiting them in real life and they usually have an interesting online shop too if they're not attached to Farfetch already. Some favourites are Graanmarkt 13, Boutique1, Tessabit, Luisa Via Roma, Flannels, Nathalie Schuterman. There's more but these are just the ones off the top of my head.