Avicenna — NotPerfect is definitely my go-to, but I’ve also had good luck with Magic Linen (I’ve only purchased housewares from them, not clothes), and Linenfox (had a very cool linen trench from them but passed it on as it was too big for me). I’d love to try LenOk Linen, Knock Knock Linen, and Son de Flor, but haven’t gotten my hands on any yet.
For US/Canada brands, I’ve gotten great linen pieces from Elizabeth Suzann, Esby, Conscious Clothing, Pyne & Smith, and Power of My People. Price point is higher, but I keep an eye out for sales /secondhand, and do a lot of trading.
My very first linen pieces were thrifted Eileen Fisher, Cut Loose, and Flax, all old-school slow fashion brands (before it was cool!) that are easy to find in secondhand shops. I had a bubblegum pink linen midi skirt with a ruffle hem — wore it to literal shreds in my college years. Turned it remnants into table napkins, which are now DS’s favorite napkins.
I’ll also say that Uniqlo makes consistently good budget linen and linen-blend offerings. Not as soft and drapey as the brands above, but sturdy enough with fun cuts and colours. I have shorts and pants from years ago that are still going strong!