I'm on Kubuntu and use
Kate for such tasks. Just tried it with a 2.1 GiB text file and it took ~8 seconds to open. Afterwards I can smoothly scroll through it. While typing it lags a little every few seconds though.
Visual Studio Code also copes well with huge files.
Both of the above load the whole file into memory though. That means if the file is larger than your free RAM, you're in trouble.
less as proposed earlier doesn't have that problem, it could also let you scroll through a 10 GB file on a system with only 1 GB RAM free.
Maybe if you could describe the specific task you're trying to accomplish with these huge files, we could propose even better solutions.