There have been some additions since 2018 when this article was written; here is the current list, from what I can tell:

  ㍳ │ 003373 │ SQUARE AU │ AU │ Australia
  ㍴ │ 003374 │ SQUARE BAR │ BAR │ Bar, Punto 2012 Sociedad Anonima Promotora de Inversion de Capital Variable
  ㎈ │ 003388 │ SQUARE CAL │ CAL │ Google
  ㏄ │ 0033C4 │ SQUARE CC │ CC │ Cocos (Keeling) Islands
  ㏅ │ 0033C5 │ SQUARE CD │ CD │ The Democratic Republic of the Congo
  � │ 01F12D │ CIRCLED CD │ CD │ The Democratic Republic of the Congo
  ㎝ │ 00339D │ SQUARE CM │ CM │ Cameroon
  � │ 01F190 │ SQUARE DJ │ DJ │ Djibouti
  ㍷ │ 003377 │ SQUARE DM │ DM │ Dominica
  DZ │ 0001F1 │ LATIN CAPITAL LETTER DZ │ DZ │ Algeria
  Dz │ 0001F2 │ LATIN CAPITAL LETTER D WITH SMALL LETTER Z │ DZ │ Algeria
  dz │ 0001F3 │ LATIN SMALL LETTER DZ │ DZ │ Algeria
  fi │ 00FB01 │ LATIN SMALL LIGATURE FI │ FI │ The Republic of Finland
  ㎙ │ 003399 │ SQUARE FM │ FM │ Federated States of Micronesia
  ㏿ │ 0033FF │ SQUARE GAL │ GAL │ Galicia, Spain
  ㎇ │ 003387 │ SQUARE GB │ GB │ United Kingdom
  ㏉ │ 0033C9 │ SQUARE GY │ GY │ Guyana
  ㏌ │ 0033CC │ SQUARE IN │ IN │ The Republic of India
  ㎏ │ 00338F │ SQUARE KG │ KG │ Kyrgyzstan
  ㎞ │ 00339E │ SQUARE KM │ KM │ Comoros
  ㏎ │ 0033CE │ SQUARE KM │ KM │ Comoros
  ㎾ │ 0033BE │ SQUARE KW │ KW │ Kuwait
  ㋏ │ 0032CF │ LIMITED LIABILITY SIGN │ LTD │ Binky Moon, LLC
  ㎃ │ 003383 │ SQUARE MA │ MA │ Morocco
  � │ 01F16A │ RAISED MC SIGN │ MC │ Monaco
  � │ 01F16B │ RAISED MD SIGN │ MD │ The Republic of Moldova
  ㎎ │ 00338E │ SQUARE MG │ MG │ Madagascar
  ㏕ │ 0033D5 │ SQUARE MIL │ MIL │ United States Military
  ㎜ │ 00339C │ SQUARE MM │ MM │ Myanmar
  � │ 01F16C │ RAISED MR SIGN │ MR │ Mauritania
  ㎳ │ 0033B3 │ SQUARE MS │ MS │ Montserrat
  ㎷ │ 0033B7 │ SQUARE MV │ MV │ Maldives
  ㎹ │ 0033B9 │ SQUARE MV MEGA │ MV │ Maldives
  � │ 01F14B │ SQUARED MV │ MV │ Maldives
  ㎽ │ 0033BD │ SQUARE MW │ MW │ Malawi
  ㎿ │ 0033BF │ SQUARE MW MEGA │ MW │ Malawi
  ㎁ │ 003381 │ SQUARE NA │ NA │ Namibia
  ㎋ │ 00338B │ SQUARE NF │ NF │ Norfolk Island
  № │ 002116 │ NUMERO SIGN │ NO │ The Kingdom of Norway
  ㎀ │ 003380 │ SQUARE PA AMPS │ PA │ Panama
  ㎩ │ 0033A9 │ SQUARE PA │ PA │ Panama
  ㎊ │ 00338A │ SQUARE PF │ PF │ French Polynesia
  ㏗ │ 0033D7 │ SQUARE PH │ PH │ The Republic of the Philippines
  ㏚ │ 0033DA │ SQUARE PR │ PR │ Puerto Rico (U.S.)
  ㎰ │ 0033B0 │ SQUARE PS │ PS │ Palestinian Territory, Occupied
  ㎺ │ 0033BA │ SQUARE PW │ PW │ Palau
  ₨ │ 0020A8 │ RUPEE SIGN │ RS │ Serbia
  � │ 01F14C │ SQUARED SD │ SD │ Sudan
  ℠ │ 002120 │ SERVICE MARK │ SM │ San Marino
  ㏛ │ 0033DB │ SQUARE SR │ SR │ Suriname
  � │ 01F14D │ SQUARED │ SS │ SS │ South Sudan
  st │ 00FB06 │ LATIN SMALL LIGATURE ST │ ST │ Sao Tome and Principe
  ㏜ │ 0033DC │ SQUARE SV │ SV │ El Salvador
  ℡ │ 002121 │ TELEPHONE SIGN │ TEL │ Contact data
  ™ │ 002122 │ TRADE MARK SIGN │ TM │ Turkmenistan
  Ⅵ │ 002165 │ ROMAN NUMERAL SIX │ VI │ Virgin Islands, U.S.
  ⅵ │ 002175 │ SMALL ROMAN NUMERAL SIX │ VI │ Virgin Islands, U.S.
  ㌽ │ 00333D │ SQUARE POINTO │ ポイント │ Amazon Registry Services, Inc.