Steps:
Disable build-in content blocker
Install uBlock Origin (firefox)
Add following to uBO custom filters. It should make YT home page display 5 (minimum) to 6 columns even on small (or narrow) screen
youtube.com##ytd-rich-grid-row, #contents.ytd-rich-grid-row:style(display:contents !important;)
youtube.com##ytd-rich-grid-renderer:style(--ytd-rich-grid-items-per-row: 6 !important;)
Goto youtube.com in a new tab, YT only displays 3 columns
Full reload with option+cmd+r (cmd+r may also works), YT display 6 columns
uBO should work on first load.
PS: This may or may not be a uBO only issue, but it is one with obvious symptom.
Version 0.99.131.1-rc (WebKit 621.1.2.111.4)
Sequoia (15)
