Never ordered from flashquark myself, but I have seen in the past that they are legit. I’ve gotten good quality PBT keycaps from Kinetic Labs with really good success. Drop have been fine for me as well.

Drop is pretty good, I got my first set (MiTo DCD Pegaso) and it was excellent quality. I got my recent set off of Keyspensory and the quality is alright, and have two groupbuys coming in from Vala Supply and Mintlodica respectively. I'm hoping those will be pretty good, though my Vala Supply order has been delayed several months now.

Also keebs.gg is handy since it lists some of the more popular keyboard sites. I've heard people have issues with Kono and occasionally kdbfans (not listed on the site) just as a note.

Divinikey is good. So is kbdfans.

I'm about to bulld my first board and would also like some info on this. Comment for visibility!

I've gotten chinese clone keycaps from Amazon, they're fine as long as you get like doubleshot and read reviews.

If you've got the money to spare or find a deal (like myself and a friend split a buy 1 get 1 free deal) check out Drop.com. A decent selection of high quality keycaps and imo are such a comfortable profile (MT3) but if you prefer a more conventional cherry profile, they carry those as well.

My daily driver at home has Drop X Noctua MT3 keycaps from drop and my work keyboard currently has some XDA Botanical clones from Amazon. Both are good, the Drop keys are better though.

Cannonkeys and Novelkeys have some good in-stock sets nowadays

Buy dye sub caps from amazon