Added

• Introduces CSS custom property --fa-width for standardized width management in stacked icons.

• We added some new icons, including:

  • a juicy new lychee icon,
  • a fancy new envelope-ribbon icon,
  • a neighborly new mailbox-open-empty icon,
  • a freshly delivered mailbox-open-letter icon,
  • a chunky new tank-recovery icon,
  • a zappy new transducer icon,
  • and a nosy new box-magnifying-glass icon.

Fixed

• Fixes a Regular Expression that caused errors in older versions of Safari when using SVG JavaScript pseudo-elements.

• Fixes content alternative (when using the content: var(--fa) CSS attribute) with Safari 14.1 specifically (and maybe others) by adding @supports to target browsers that support it.

• Fixes a Windows font family grouping problem when using OTF Desktop files.

• Fixes style-only (no family specified) icon CSS classes not rendering icons when using dom.watch().

• Fixed a number of icon-related issues:

  • Fixed issue with where our beta and rectangle-high-dynamic-range icons were missing some Duotone fills.
  • Fixed a missing cutout in the Solid styles of our screwdriver-wrench icons.
  • Our new stadium icon in Sharp Solid was showing the wrong style.
  • Our pencil, pencil-line, and motorcycle icons had the wrong fills in some Duotone styles.
  • The cheese-swiss icon had a few too many holes glitches.
  • Fixed our Duotone mango icon.
  • Fixed issues with our box-arrow-down-magnifying-glass and box-arrow-down-arrow-up icons.
  • Removed extra bars in our signal-weak icon.
  • Fixed a missing fill in the Regular style of our dot-circle icon.
  • Fixed issues with envelope-open-dollar, filter-circle-dollar, and filter-circle-xmark.

Changed

• Solved the case of the shriking checkmarks and adjusted the sizing and legibility of all of our icons that contain a check.
• Took a similar approach and tweaked the design of our exclamation icons.
• Updated the design of our stretcher icon to look more like a stretcher.
• Adjusted the design of our peruvian-soles icons to remove the outdated dot.
• Remapped the design of our oil-temperature icon to a new water-temperature and redesigned the original.

Source: https://fontawesome.com/changelog