Excessive video buffering on a minimal laptop running Ubuntu 18.04
These system firmware updates can simply be transferred to a FAT-formatted USB drive and can be performed from the firmware according to Dell's own instructions (see the section called "Installation Instructions") provided with the firmware. There is a "BIOS Update" option available within the one-time boot device selection menu, found by pressing F12 during POST. You can then select the file from the drive using the arrow keys.
I don't know if this will help resolve your buffering issues, however.