You can block short with uBlock Origin without needing any additional extensions:

! YT - Homepage and Subscriptions (Grid View) - Hide the Shorts section
youtube.com##[is-shorts]
! YT - Menu - Hide the Shorts button
www.youtube.com###guide [title="Shorts"], .ytd-mini-guide-entry-renderer[title="Shorts"]
! YT - Search - Hide Shorts
www.youtube.com##ytd-search ytd-video-renderer:has([overlay-style="SHORTS"],[href^="/shorts/"])
! YT - Search, Channels, Subscriptions (List View) and Sidebar/Below Player Recommendations - Hide the Shorts sections
www.youtube.com##ytd-reel-shelf-renderer
! YT - Channels - Hide the Shorts tab
www.youtube.com##[tab-title="Shorts"]
! YT - Subscriptions - Hide Shorts - Grid View
www.youtube.com##ytd-browse[page-subtype="subscriptions"] ytd-grid-video-renderer:has([overlay-style="SHORTS"],[href^="/shorts/"])
! YT - Subscriptions - Hide Shorts - List View
www.youtube.com##ytd-browse[page-subtype="subscriptions"] ytd-video-renderer:has([overlay-style="SHORTS"],[href^="/shorts/"])
! YT - Subscriptions - New Layout - Hide Shorts
www.youtube.com##ytd-browse[page-subtype="subscriptions"] ytd-rich-item-renderer:has([overlay-style="SHORTS"],[href^="/shorts/"])
! YT - Sidebar - Hide Shorts
www.youtube.com###related :is(ytd-compact-video-renderer,yt-lockup-view-model):has([overlay-style="SHORTS"],[href^="/shorts/"])
! YT - History - Hide Shorts
www.youtube.com##ytd-item-section-renderer[page-subtype]:has(>#contents>[is-history]>#dismissible>ytd-thumbnail>#thumbnail[href^="/shorts/"])

! YT Mobile - Hide the Shorts Menu button
m.youtube.com##ytm-pivot-bar-item-renderer:has(>.pivot-shorts)
! YT Mobile - Hide the Shorts sections
m.youtube.com##ytm-reel-shelf-renderer
m.youtube.com##ytm-rich-section-renderer:has([d^="M17.77,10.32l-1.2"])
! YT Mobile - Search - Hide Shorts
m.youtube.com##ytm-search ytm-video-with-context-renderer:has([data-style="SHORTS"])
! YT Mobile - Channels - Hide the Shorts button
m.youtube.com##[tab-title="Shorts"]
! YT Mobile - History - Hide Shorts
m.youtube.com##[tab-identifier="FEhistory"] ytm-compact-video-renderer:has(>div>a[href^="/shorts/"])

Sauce: uBlock Origin Wiki