You can use ublock origin browser extension per-site CSS rules to restore an arbitrary number of rows and columns to the youtube frontpage. https://old.reddit.com/r/uBlockOrigin/wiki/solutions/youtube is a good source for these if you don't know how to write them or don't want to.

    ! YouTube frontpage - 3 columns per row
    youtube.com##ytd-rich-grid-row, #contents.ytd-rich-grid-row:style(display:contents !important;)
    youtube.com##ytd-rich-grid-renderer, html:style(--ytd-rich-grid-items-per-row: 3 !important;)
    youtube.com##ytd-rich-grid-renderer, html:style(--ytd-rich-grid-posts-per-row: 3 !important;)

    ! Optional: Hide the "Shorts" section to maintain clean 3x3 grid
    youtube.com##ytd-rich-section-renderer:style(display:none !important;)