OP has my every sympathy… Mine’s got a clunk, you can hear it and feel it on the non-drive side as you pedal, it’s every stoke but effected by load, BUT it’s not at the same point of every stroke.
Even though there was zero play in the BB, it wasn’t spinning well so I changed it, clunk went… for about 3 rides, now it’s back!
Gave up and handed it over to a Pro, I’m inline for a new chain and cassette anyway – which might fix it I suppose – they’re pretty worn it seems. I fear it might be the chainset though, I foolishly rode it once when it wasn’t on tight enough and the arm fell off, it’s never been right since