There are a lot of Befunge-93 Ruby implementations in the wild but I don't see any Befunge-98.
So let it be the first one.

• Befunge-93 ("Befunge-93 Documentation")
• memory size and code format edits
• Befunge-98 ("Funge-98 Final Specification")
  • operations
    • q -- quit
    • a-f -- push 10..15 onto stack
    • n -- clear all stacks
    • ', s -- fetch and store a char
    • ; -- comments
    • ], [, w, r, x -- change delta
    • j -- jump forward
    • k -- iterate
    • {, }, u -- push cells between TOSS and SOSS
    • (, ) -- we don't implement semantics
    • y -- what do 13th and 14th slots mean?
    • z -- can we just skip it?
  • y specification allows us to skip these
    • (execute) =
    • (filesystem) i, o
    • (concurrent) t
    • (3D) h, l, m
• tests
  • bin
    • Hello, World!
    • failures, ^C, hanging, etc.
  • operations
    • Befunge-93
      • @
      • "
      • 0..9
      • $, :, \
      • #
      • >, <, ^, v, ?
      • +, -, *, /, %
      • |, _
      • ~, &, ,, .
      • !, `
      • p, g
    • Befunge-98
      • ~, &
      • q
      • a-f
      • n
      • ', s
      • ;
      • w
      • ], [, w, r, x
      • j
      • k
      • {, }, u
      • (, )
      • y
      • ...
• Github Actions test
• gemify
• announce

This implementation in another language somewhat helped me: https://bitbucket.org/lifthrasiir/pyfunge/src/default/funge/languages/funge98.py