“According to” causes all sorts of problems.
So creating a whole list of ‘synonyms’ that aren’t really synonyms is only going to make matters worse.
Although some of the ‘synonyms’ listed below are grammatically correct and closely connected to the meaning of ‘according to’, they are rarely used in the same contexts.
'According to' refers to an opinion which is not the speaker’s opinion. It usually occurs at the start of a sentence.
'According to' is often used in formal contexts to refer to official evidence such as statistics or reports:
⚠️"According to me"* is wrong and can NOT be used instead of "In my opinion".