I got one from a brand called "Moustache" which are very good quality.
They do a range of them although I went for one much dearer than 2k😳. I went a bit mad but paying it interest free.
I would say get one with the biggest battery you can afford..... You will need it if you want to do 50mile rides.
As I live in a very hilly place I went for one with the most powerful motor available......known as the Tork in the descriptions. . That's the oomph from the motor. At the time that was 75 oomphs! (cant remember the units!). There are now 85 oomph models available).
My longest ride is 42 miles so far and that included 2 massive hill climbs several miles long, and I still had around half my battery left. I did eke it out by using hardly any assistance on the flat though. These are not trips I could even have contemplated on a non ebike.
Also think what you want to do with it... City, tracks, off road etc.
Mine is a hybrid. Fine on the road but tough enough for tracks etc. Enough suspension to be comfy.
My friend has a, folding one, a definite town bike. Only 50oophs in the motor. It's really good but struggles where I live with the steep hills. You really notice the lack of power. It does get you up but it's hard work. It also has a much smallerbattery.
It wouldn't do for longs rides in the hilly place I live. With all the hills it's range drops to less than 20miles.
Look at the components. Decent bikes mainly have Bosch motors. They are best to have the motor center mounted rather than the back wheel.
Moustache are ebike specialists, they don't do normal bikes. I like mine, it's been perfect for a year.
Another brand which had the spec I was looking for, and were actually a bit cheaper, and with good reviews, were Cube (or is it Kube?). I just couldn't get one near me to try it and they aren't as nice a shape (and didn't have nice colours😂).