Some people reported they were able to run Catalina on i5-10210u and i7-10510u. For now, the biggest problem is the i7-10710u that is a six cores CPU.
However, all this people claiming to have a working hack with a 10th gen had to spoof the cpu so Mac recognize it as a previous model. I pretty much doubt it really works as it should. Anyway, having added support for 10th gen on beta, makes Catalina to support those processors soon in the public version, even the six cores i7 model. If you will make a purchase, go for the 10th gen.
If you will use Windows too, maybe you care about those models with a GTX included. I don’t because I only use Mac, and as you know, GeForce graphics are useless there.