I also wore Birkenstocks and DMs. I have a pair of Groundies Universe and they are slightly too small in length I think and very wide, though without the weird barefoot shape. I'd go up a size but suspect they'd look ridiculously wide then.
Not sure why I've not tried be lenka, it's either the width/shape of the sole or the thinness. I'd have to look them up.
Totally agree though about the Groundies. They look like normal shoes.
DS has a pair of merrell trainers that I wish I'd bought for myself.
My half size length and width issue happens in conventional shoes too, it's not confined to barefoot!
Rocket Dog Jazzins are considered barefoot friendly. I think they were better but now have a padded insole that needs to be replaced with something flat and has to be ripped out somehow. But cheap to try out - always loads on mandm direct. There are cheaper barefoot shoes on Amazon too. I try not to buy from there though. I've been looking at Mukishoes for an ethical, environmentally sustainable option. They do a cork insole to add to the stack height.
There's a Spanish website (Google barefoot shoes Spain) that gives all the stack heights of what they sell.
not obsessed at all
It's a pain buying everything online but I suppose that's the case for everything now due to the pandemic.