Reference: SharePoint Online Language IDs

This is a list of languages that SharePoint Online supports and the codes to represent them:

NameLanguage TagLCID
Arabicar-SA1025
Azerbaijaniaz-Latn-AZ1068
Basqueeu-ES1069
Bosnian (Latin)bs-Latn-BA5146
Bulgarianbg-BG1026
Catalanca-ES1027
Chinese (Simplified)zh-CN2052
Chinese (Traditional)zh-TW1028
Croatianhr-HR1050
Czechcs-CZ1029
Danishda-DK1030
Dariprs-AF1164
Dutchnl-NL1043
Englishen-US1033
Estonianet-EE1061
Finnishfi-FI1035
Frenchfr-FR1036
Galiciangl-ES1110
Germande-DE1031
Greekel-GR1032
Hebrewhe-IL1037
Hindihi-IN1081
Hungarianhu-HU1038
Indonesianid-ID1057
Irishga-IE2108
Italianit-IT1040
Japaneseja-JP1041
Kazakhkk-KZ1087
Koreanko-KR1042
Latvianlv-LV1062
Lithuanianlt-LT1063
Macedonianmk-MK1071
Malayms-MY1086
Norwegian (Bokmål)nb-NO1044
Polishpl-PL1045
Portuguese (Brazil)pt-BR1046
Portuguese (Portugal)pt-PT2070
Romanianro-RO1048
Russianru-RU1049
Serbian (Cyrillic, Serbia)sr-Cyrl-RS10266
Serbian (Latin, Serbia)sr-Latn-RS9242
Serbian (Latin)sr-Latn-CS2074
Slovaksk-SK1051
Sloveniansl-SI1060
Spanishes-ES3082
Swedishsv-SE1053
Thaith-TH1054
Turkishtr-TR1055
Ukrainianuk-UA1058
Vietnamesevi-VN1066
Welshcy-GB1106

If you would like to generate this list for your use, please see my script on PnP Script Samples: Generate Markdown Report of LCIDs | PnP Script Samples