Slow internet on LINUX MINT?

Question

linux

- 8 gigs of RAM, 2600k intel, blue HD for 2tb - USB
modem, router is not worth it
- 4G MIMO antenna is on the roof
- in Windows (two OS on a computer) everything is fine with speed
There was Windows, the Internet was good. I installed Ubuntu - the Internet became slow, moved it to Mint, also slow. Remarkably, when sitting from a flash drive (ubuntu was on a flash drive), the Internet worked well, at x2 speed it loaded 720p YouTube videos. Now 480 barely pulls. Winda used to be on the SSD, but it's unlikely that it decides.
I found on the Internet one of the solutions to a similar problem, it was necessary to disable ipv6. Disconnected, nothing has changed (yes, earlier the sixth one was in ipconf, and after cleaning it stopped, but it was not decided). Computer restarted - nothing.
New to Linux.

Answer 1

USB modem... direct wire to computer

So USB modem or twisted pair?
Throw off the output of lspci , if a direct wire to the computer , if the USB modem then lsusb . Show more /etc/resolv.conf . What browser do you use?