You didn’t tell us anything precise about your needs and possibilities. What is cheap for you? “Cheap and fast” is definitely impossible. How about buying a cheap one and upgrading it later? (I did it with my Librem 15 and happy) Do you need a GPU passthrough? Do you require many USB controllers? Do you prefer a free BIOS (coreboot)? Heads?
In general, there are already many topics like this on the forum, try to search for “new laptop” or something.
Most importantly, there is a Community recommended list: