DM me. with one unique identifier, could be his primary email, work email, cell, or even a secondary email. (ideally one that he uses often). If he does not have an online footprint, some cheaters don't, and use aliases, others do it so brazenly that you don't suspect.
That is all I need, and do NOT post it here. Do NOT tell me who you are or who he is. Or post it anywhere public. If he is tech savvy then maybe I might need more, address and DOB or usernames.. and will come back to you, if so.
The problem with cheaters is, even the very very best cheaters, sadistic, narcissistic psychopathic who believe their own alternate reality because that is the only one they have known with the best skills.. It will eventually get caught because cheaters cheat and it is the thrill of cheating that excites them
I have done many cases where the cheating happens the most, when the relationship was at '"good times". And these types, can be hard to detect but trust your gut feel and once I see the patterns, they become so predictable that it is almost like clock work.
The hardest to catch is the remorseful one time cheats who are tech savy. Because they will put their skills to work and will leave no trace or can cover their footprint.
I will start with passive recon (i.e no one will know except you and me). And see what I get and then check in with you after if it is ok to do active recon. Just by years in doing this first to help friends as a hobby. The patterns are predictable, human nature is itself predictable and cheaters or deniers (subconsciously insecoure, feels superior because they think they have outsmarted everyone and they usually did, until they don't). They are very very good because of years of practice and signals are very difficult to decipher at first but once you crack it it becomes obvious. They are masters at manipulation, and planning and trying to cover their tracks. You can literally see their devious brain working and planning ... and it becomes so brazen, that the victim is often left traumatic.
Well, I do have are a very particular set of skills. Skills I have acquired over a very long career. Skills that make me a nightmare for people like your SO. If he comes clean, that will be the end of it. I will not look for him, I will not pursue him. But if he doesn't, (with your permission I will look for him, I will find him and I will leave it you if you want to DOX him.
The one time or some of the time cheaters/affairs with remorse, will have different storyline each time which makes it interesting and because it is unplanned. But wait, how do I find out anything if he /she has done it and turned a new leaf .... you may ask?
Often I have targets who are actively covering their tracks which in my opinion is pointless because cheaters are just like casino gamblers/addicts. They know the odds and they can be rational but just not
Lastly, and when the SO feels the need to gather evidence, trust your first gut feel, and then double/shorten that time line. i.e in a 3 year relationship, if you think they started cheating at the 2 year mark and, well they probably already did at the 1 year mark.
For serial cheaters, it is that thrill that excites them.. the need for constant validation becomes a survival to them. Their childhood left them so broken (they cannot see this or choose not to), (these will get caught eventually give it time).. and will only stop when presented with total irrefutable evidence. But don't expect remorse or a sorry. Take comfort in knowing deep down, they do feel too but just
Just DM me (if you prefer without encryption, I'm ok with that, But if you DM me your pgp public encryption key, and want to go down that route, no issues too) , it appears to me you are crypto savvy so..i have a rough gauge already.. maybe I can offer complimentary skills or we can get lucky
I do this for free if it is a quick job, and will let you know if I need to dedicate resource on it with a reasonable pricing. Or I can't do it in a specific time frame. You need to later decide to tell me how far you want to go, and as early as possible if you want this to go for litigation support. Methods may defer.
because of my childhood, I saw one parent treat the other parent and knew there were certain values that I will stand for and some against.