Spotify maintains a support document listing the countries where it is available:
https://support.spotify.com/us/article/where-spotify-is-available/
Last updated on 22nd April, 2022 (at time of writing).
Javascript console snippet to extract the list of countries:
console.log(Array.from(document.querySelectorAll("li:not([class])")).map((e) => { return e.innerHTML }).sort().join("\n"))This gives us the following list:
Albania
Algeria
American Samoa
Andorra
Angola
Anguilla
Antigua and Barbuda
Argentina
Armenia
Aruba
Ascension
Australia
Austria
Azerbaijan
Azores
Bahamas
Bahrain
Balearic Islands
Bangladesh
Barbados
Belarus
Belgium
Belize
Benin
Bermuda
Bhutan
Bolivia
Bonaire
Bosnia
Botswana
Brazil
British Virgin Islands
Brunei Darussalam
Bulgaria
Burkina Faso
Burundi
Cambodia
Cameroon
Canada
Canary Islands
Cape Verde
Cayman Islands
Ceuta
Chad
Chile
Christmas Island
Cocos (Keeling) Islands
Colombia
Comoros
Cook Islands
Costa Rica
Croatia
Curaçao
Cyprus
Czech Republic
Côte d'Ivoire
Democratic Republic of the Congo
Denmark
Djibouti
Dominica
Dominican Republic
Ecuador
Egypt
El Salvador
Equatorial Guinea
Estonia
Eswatini
Falkland Islands
Faroe Islands
Fiji
Finland
France
French Guiana
French Polynesia
Gabon
Gambia
Georgia
Germany
Ghana
Gibraltar
Greece
Greenland
Grenada
Guadeloupe
Guam
Guatemala
Guernsey
Guinea
Guinea-Bissau
Guyana
Haiti
Honduras
Hong Kong
Hungary
Iceland
India
Indonesia
Iraq
Ireland
Isle of Man
Israel
Italy
Jamaica
Japan
Jersey
Jordan
Kazakhstan
Kenya
Kiribati
Kosovo
Kuwait
Kyrgyzstan
Lao People's Democratic Republic
Latvia
Lebanon
Lesotho
Liberia
Libya
Liechtenstein
Lithuania
Luxembourg
Macao
Madagascar
Madeira
Malawi
Malaysia
Maldives
Mali
Malta
Marshall Islands
Martinique
Mauritania
Mauritius
Mayotte
Melilla
Mexico
Micronesia
Moldova
Monaco
Mongolia
Montenegro
Montserrat
Morocco
Mozambique
Namibia
Nauru
Nepal
Netherlands
New Caledonia
New Zealand
Nicaragua
Niger
Nigeria
Niue
Norfolk Island
North Macedonia
Northern Mariana Islands
Norway
Oman
Pakistan
Palau
Palestine
Panama
Papua New Guinea
Paraguay
Peru
Philippines
Pitcairn Islands
Poland
Portugal
Puerto Rico
Qatar
Republic of the Congo
Romania
Rwanda
Réunion
Saba
Saint Barthélemy
Saint Helena
Saint Martin
Saint Pierre and Miquelon
Samoa
San Marino
Saudi Arabia
Senegal
Serbia
Seychelles
Sierra Leone
Singapore
Sint Eustatius
Sint Maarten
Slovakia
Slovenia
Solomon Islands
South Africa
South Korea
Spain
Sri Lanka
St. Kitts and Nevis
St. Lucia
St. Vincent and the Grenadines
Suriname
Svalbard
Sweden
Switzerland
São Tomé and Príncipe
Taiwan
Tajikistan
Tanzania
Thailand
Timor-Leste
Togo
Tokelau
Tonga
Trinidad and Tobago
Tristan da Cunha
Tunisia
Turkey
Turks and Caicos Islands
Tuvalu
Uganda
Ukraine
United Arab Emirates
United Kingdom
United States
United States Minor Outlying Islands (Navassa Island, Baker Island, Howland Island, Jarvis Island, Johnston Atoll, Kingman Reef, Midway Atoll, Wake Atoll)
United States Virgin Islands
Uruguay
Uzbekistan
Vanuatu
Venezuela
Vietnam
Wallis and Futuna
Zambia
Zimbabwe
Åland
At the time of writing, Russia is not included in the list of countries, but users who had subscriptions before it was removed continue to have access.