https://api.bridgedataoutput.com/api/v2/OData/har/Properties?$filter=toupper(StreetName) eq 'MAIN'&$top=10&$select=ListingKey,BedroomsTotal,StreetName,StreetNumber,City,PropertyType,ModificationTimestamp,ListAgent,CloseDate,StreetName
Convert a string to upper case (toupper). Lower case would use the function tolower().