Well that's an interesting topic, to begin with, and the short answer is it depends.
There are several factors affecting my response, it depends on the following staff:
1. Casino owner - RTPs are usually provided by the game providers mostly, they are aiming at a golden ratio, but they have few options to choose from. for example, if you are a casino owner and want to have lower RTP on your website compared to others, you can ask a provider to do that, and they will lower the RTP specifically for you. RTPs that are publicly available are usually not applicable to all online casinos since they are being modified based on the request of the owner.
2. Provider - or rather is the provider Licensed? and who licensed them? there are several neutral organizations granting these licenses, and which license do they have? In most cases, if the provider wants their game to be legal in some market or other, they need to receive an iGaming license for the market, and in order to receive the license, they (including other things) need to have RNG License which basically says their games aren't rigged, and results are random. Most of the games you play are from bigger slots providers. Thus, they are licensed and have RNG certificates. Game providers such as
netent.com,
pragmaticplay.com,
https://www.yggdrasilgaming.com/Upgaming.com are licensed and safe to play, but there is 3rd deciding factor as well.
3. Casino Reliability - As you might know, most of the casinos nowadays aren't licensed; for some markets, even the games aren't licensed; if you come across some suspicious online casino, you might or might not notice a difference in the games they have on their websites, what they are doing is basically stealing the games and redeveloping those by themselves putting their own math behind them. I have come across to one of
upgaming.com's games that was stolen in some market; the games stolen were Dino, Chicken, and some others as well. So basically, that casino didn't want to pay the company share of their profits so they stole the design redeveloped the game, put their math behind it, and possibly rigged them as well.
So short answer is this: if you are playing on a licensed casino, then it's not rigged (they may have different RTPs, but they aren't rigged), but if you are playing on a casino that's not licensed, you never know. usually, it's not so profitable to steal the games. It takes time and human resources for casinos to do that, but in some cases, they are stolen and rigged mostly on suspicious websites.