そうだ

そうだ relays a specific report almost word for word. らしい blends hearsay with a guess, staying vague about where it came from.

によると always names the source of the information (天気予報てんきよほうによると). そうだ can relay hearsay with no source named at all (今日きょうは雨あめだそうだ).

そうだ hands the claim to whoever said it, open to 誰だれが. たぶん keeps the guess as the speaker's own, answering only to 何なにでそう思おもうの.

そうだ passes on information without naming its source, forecasts and rumor alike (天気予報てんきよほうによると…そうだ). と言いっていた pins the words on a nameable person, open to challenge.

ということだ can take a real past ending (ということだった), unlike hearsay そうだ. そうだ stays spoken, and ということだ leans toward written reports.

という at a sentence's end belongs to written narration, citing no source (明治めいじの頃ころは宿場町しゅくばまちだったという). そうだ is the everyday spoken choice, and usually has a source, named with によると.

そうだ passes on one thing said once, usually naming the source right there (天気予報てんきよほうによると). 言いわれている names no occasion, and reads like a written, general claim.

そうだ backs the wording and ends the sentence (風邪かぜをひいたそうだ). とかで softens the reason mid-sentence instead, feeding into what comes next (風邪かぜをひいたとかで欠席けっせきした).

そうだ has no past or negative form of its own. と聞きいている freely takes both (聞きいていません, 聞きいていましたか), and names its source with から where そうだ needs によると.

そうだ passes on anything secondhand, read or overheard. とのことだ names an identifiable source with より／から (部長ぶちょうより…とのことです), which そうだ cannot.

そうだ has its own polite step (そうだ→そうです, still hearsay). って has none, more formality means switching to という／とのことだ.

Plain-form 降ふるそうだ relays what someone said ("I hear"). The ます-stem form 降ふりそうだ instead reads the sky, one kana apart.

と思おもう puts the claim in your own head (来くると思おもう is an opinion). そうだ puts it in someone else's mouth instead (来くるそうだ is a relayed report).